Discipline Priest

                 Discipline Priest is overlooked by many. Those who play Disc will often be called "useless" healers because the heal count is low. Others will mock you saying Disc is for pvp and proceed to ask the Leader to kick you from raid. But Disc is more than a healer, it's a real "health" giver, as shields raise the target's fortitude momentarily, increasing the maximum damage it can take. Those who know best understand how broken is Disc and how useful is in every raid, regardless of the boss' mechanics.

Let's go first by saying you can't play Disc as you play your regular healer. Disc is meant to protect, to act before the damage has been inflicted. First we'll go by the talent specs you can use:

Dungeons:

This spec is best suited for dungeons, where you will rarely face party-wide damage. Your main focus is keeping Power World: Shield (PW:S) on the tank and just Penance/Renew/Flash Heal as you need. Foes in dungeons don't have much health so Reflective Shields is there to do its part. One point in Grace is enough since you won't turn that much to your party to heal them, just keeping them shielded is enough, unless the tank can't keep aggro off them, but that's a different story.

Raids:

 

This spec is better suited for raiding. At higher gear levels your PW:S will be much stronger than 1 Renew (Instant protection vs a "will help you slowly" spell), so you're better off spending one GCD shielding.

• Aspiration 2/2: This mainly to use Penance more often and to give Power Infusion to that Mage/Warlock doing tons of damage at least 3 times per boss fight. Both your Pain Suppression and Inner Focus will mostly be used once per fight.
• Focused Will 3/3: This is really just to ditch points as 3% critical increase means more chances to proc Divine Aegis.
• Improved Flash Heal 0/3: Since you're using Penance more often, Flash Heal gets relegated to "will use if necessary", that won't happen often unless your raid setup requires you to, more info on this later.
• Desperate Prayer 1/1: It's a real lifesaver as it allows you to instantly heal yourself while moving. Disc is a high mobility healer and this helps towards that.
• Holy Reach: This might seem only useful for Holy Priest but that's a wrong assumption. Depending on your raid setup you might be needed to do raid-wide healing and relying on your Prayer of Mending (PoM) alone won't help much there. One Borrowed Time (BT) buff will boost a prayer of Healing's spell haste by 25%, making it even more reliable for disc than Holy (Since holy has to stack up Serendipity and that requires at least 2 GCD with Flash heal or 1 with Binding Heal to get a similar 24% haste for it). Since you keep the most of the raid shielded with PW:S you will have lots of BT to use and this just makes your Prayer of Healing more effective for spread fights.

Major Gyphs:

Recommended:

• Penance: Penance is unarguably the best single target heal a Priest can pull off and this glyph allows you to use it more often.
• Power Word: Shield (PW:S): This is the spell you cast the most so using its glyph seems reasonable. The heal amount is small but this is actually good since it won't cause overheal, making it somewhat effective.

Situational:

• Glyph of Prayer of Healing (PoH): If you find yourself more and more doing raid healing or if an encounter has a lot of raid damage, this glyph might just be what you're looking for. Even better if you picked Holy Reach talent.
• Glyph of Flash Heal (FH): If you're up for Tank healing duty this is the glyph you need, as Penance although very good, it won't keep up with the Boss' damage on the tank, forcing you to Flash Heal. FH is not very cost friendly and this glyph helps there.
• Glyph of Renew: Renew is not great for Disc, mostly because it can't crit therefore it can't give any shield, also deep Holy has the best talents to make it a more worth GCD. If you're doing 10 modes and everyone has Weakened Soul (WS) effect and your Prayer of Mending+Penance are on cooldown, you might as well use Renew.
• Hymn of Hope: It just gives that 20% bonus mana pool for another 2 seconds, the amount of charges remain the same, a pretty meh glyph.

Minors:

• Shadow Protection: Useful in every raid.
• Fortitude: Buffed stamina to the guy that just got resurrected or did your Stamina buff a second before tank pulled? This one is somewhat useful.
• Shackle Undead: Disable a foe from a safe distance? This is WotLK, undead errwhere.
• Levitate: ???

Stat prios

As a healer your main concern must always be having enough resources to do your job, that is having enough mana reserve. As you start your Disc adventure you first want to have enough mana reserve for the dungeons you will farm. Whilst you can stop and drink to refill your mana, doing it after every group of foes will slow down your group considerably, and you don't want that in a party with random strangers, oh no...

Low gear: Intellect>Spirit>Spell Power.
              Reds: Runed.
              Yellows: Brilliant.
              Blues: Sparkling.

You can mix those stats as you please with Purple/Orange/Green gems but try to follow the prios. As you get better gear (after an average of 232) you change your prios to the following (slowly as you progress your gear):

Mid/Higher: Spell power>Intellect>Spirit.
               Reds: Runed.
               Yellows: Luminous.
               Blue: Purified.

The focus changes entirely to Spell power, as your main spell (PW:S) scales greatly with your Borrowed Time talent.

Haste or Crit?

Haste and Critical are regular Dps stats and heals don't usually rush items with them. The reason behind this is simple: In spite of heals getting stronger, your overheal also increases which is wasted mana, thus making you an ineffective healer. Another reason is, dps have many tools to get back big amounts of mana, and even if they do go oom the raid won't notice much because there are many dps in a raid, contrary to only 5 healers; losing 1 heal means 20% less raid healing, if the healers are doing a similar job overall.

Taking that into account, healers prioritize mana reserves until the gear is very good. Regarding Disc things are a little different. First of all your haste gets capped rather easily (154 haste for a 1 second GCD if you have 3% aura and 5% from totem) due to BT. Almost every weapon in Icecrown Citadel and Trial of the Crusader has haste in it and 2 out of the 5 T10 pieces have haste, therefore your haste soft cap will be reached without issues. Crit is a fine stat and gives you more chances of using Divine Aegis, the only problem with crit is that your only real heals are Penance and Prayer of Mending, the shield from your PW:S can't crit, therefore Crit is not a stat that you'd seek much. With this in mind, you can easily figure out that although haste is important before 154, it loses importance rather quickly, while crit continues to be useful and has no real cap thanks to Divine Aegis. So in case you have two items with same ilvl, one crit and the other one haste, you can pick wisely now.

Intellect or Spirit?

If your mana suffers, Intellect is the way to go as Disc. Spirit should just come in your gear and maybe from Purified purple gems. If you need more reassurance, keep reading.

Rapture

This talent is probably the best mana source generation effect after replenishment (yes, you heard me Paladins and your Divine plea). It seems a little lackluster because it's only 2.5% on you when the shield breaks and 2% on the shielded target (along the other resource types), but the truth relies in the numbers...The cooldown is 12 seconds, this means you have 5 sure procs if you use them on tanks and other targets taking heavy damage, that gives you 15% of your total mana, without the need to lose 50% of your healing done. Not just that, although the cooldown presumably only allows one proc every 12 seconds, if two of your shields break at the same time you get twice the amount (5%) in a single proc, or three times the amount if three break, or... you get the idea. Multi procs are hard to master but if you know the encounter it shouldn't be that complicated. This is another reason why you shouldn't reapply your PW:S; just let it break and give you mana!

Pro tip: You can use lower rank PW:S to achieve this Rapture multi proc, although it is very hard to master.

How do I know an item is an upgrade?

Remember the stat prios. Let's consider Item X. Does X have haste? Your cap is 154 with all haste buffs considered (not Heroism/Bloodlust considered); if X has no haste points and you are haste capped then you can consider X an upgrade if the ilvl is higher than your current item (and of course if you're not replacing an item with haste). The next thing to check for is the mana regeneration stat, because if it lacks haste then it must have mp5 or Spirit in it; obviously Spirit is the preferred stat, but if you can't find anything else in that slot, then mp5 will have to do. Better items (213 and above) have an additional stat, if the above conditions are met then that stat will be Critical; this one is fine since it favors your Divine Aegis. Congratulations, you can use X!

  A little Theorycrafting

A lot of people believe haste and crit are very important stats for a disc, and even forgo stats with spirit to use a haste/crit item. For all those people I can only say 1 thing: You fail. Well, now that I have your attention I'll just explain with numbers (because numbers don't lie).

First of all, establish a rotation; if you look at the most used spells their cooldowns are low (10s PoM and 8s Penance), so in a 10s span, you will do 1 PoM, 1 Penance and the rest of the time you will fill with PW:S. Penance is actually around 1.35s with your haste cap and other haste buffs, so we have:

• 7 Power word: Shield (7 seconds)
• 1 Prayer of Mending (1 second)
• 1 Penance (1.35 seconds)
• Waste time: .65 seconds (If your latency is not close to 0, you can consider this time as Latency)

Eventually you will use two penance in a 10s span because it has 8s cooldown, that's where that .65s fills in (Or latency). Now that you know what you're doing let's see the stat benefits:

                                                              Benefits from

       Spell name              Spell Power            Haste           Critical

Power Word: Shield           Yes                       No                 No

Prayer of Mending             Yes                       No                 Yes

Penance                           Yes                      Yes                 Yes

A note on Penance crits: You really just need one of the ticks to crit, two crits is a waste because on average a boss does 1 auto attack every 2 seconds; but a tank won't take damage every 2 seconds, this timer will be increased further by factoring in avoidance stats, making it somewhere between 3 seconds depending on the tank. More than 90% of the time the first critical heal from Penance will be overwritten by the second critical before it does its part, therefore although Penance can crit, only 1 crit will be helpful, the rest will be overheal or waste. Run the math if you don't believe me: 3 ticks in 1.35s means a tick every .45s, no tank will take damage that fast. Anyway, the real benefit from Penance crit is putting Inspiration buff (and Grace) on the tank, the absorb will be a meager ~2k that will be gone with literally any source of damage. (40% crit is enough for Penance to crit at least once, you get this fairly easy if you respect the stat prios I mentioned before and the usual raid buffs you get from other classes). 

Another thing worth mentioning is, although the PW:S glyph heal can crit, whether it does or not won't make a noticeable difference in the heal meter, in other words, you don't cast PW:S for the heal from glyph, you do it to PROTECT people. Always keep that in mind.

Ok then, having this in consideration, we come to the realization that 70% of our spells cast in a 10s span don't benefit from haste and crit stats, and from the 30% remaining, 10% benefits fully from crit but not from haste, and the last 20% benefits fully from haste but just mildly from crit. 

Quantifying this even further, we have a 100% benefit from spell power, 30% from crit and only 20% from haste; this means every time you stack haste beyond the cap you're getting only 20% benefit from it, and only 30% benefit from crit. This is why spell power is king, followed by intellect to cast nonstop. Critical heals cause overheal but since you have Divine Aegis, it is accepted that Critical is superior to haste, at least slightly due to this.


Last thoughts regarding stats and gear:

Generally, your only worry is keeping that haste stat at 154 or just a little above it in case you don't have the other buffs (433 without any external aura/totem). Dungeons don't matter much, or at least not for long, so while you're in that stage haste is a whatevs stat. In a raid, missing those buffs is a huge pushback in raid performance; missing a shaman is also missing Heroism/Bloodlust so generally the shaman will be present in most 10modes. Retribution or Balance may not be present in a 10 mode but almost every 25mode will have at least one of these. If you want to set your haste to 256 (if only 5% totem is present) for 10 modes that's fine too, just don't sacrifice spell power to have this rating.

At very high gear, I'm talking about full 25n modes geared, your mana reserve becomes so good you can even modify your rotation a little and use Prayer of Healing regularly. The reason you didn't do this before is due to the high cost of the spell, but at high gear (or should I say high intellect) you stop worrying about that; remember to use it with a BT charge.

Playing Disc

Now that you have your desired talent spec and you are aware what Disc needs to gear you will learn how to play Discipline. Like I said before Disc plays, preferably, before damage happens. PW:S is your bread and butter; let's say it shields for 10k damage on average, that means that for 30 seconds you are increasing a target's health by 10k, thus making everyone mini tanks... amazing!

It's no surprise when Disc is treated as a raidwide protector, as raising a target's health by ~30% (non tank) seems more plausible than raising another one's by merely ~15% (on an average tank) or less. The 2 T10 bonus tried to help Disc a little by giving Flash Heal a nice hot, but still Disc will be better by focusing on the raid rather than only on the tank(s).

There is a priority as to how you will use your precious GCDs:

1. PW:S on tank(s), always. Same applies to anyone else with heavy damage on them. Don't reapply it before it breaks, let your Rapture talent do its job.
2. PoM always on cooldown. To make sure it triggers asap use it on the tank following a PW:S, or someone that is about to take heavy damage enough to break the PW:S you supposedly dropped before.
3. Penance on whoever has less than half health, or use it on the tank taking the most damage. This works like your PoM except for single target, it does 3 ticks (jumps in the case of PoM) and each one can crit and add a shield. It's important that you have this on cooldown all the time if damage is being taken that goes beyond your shield in a rather fast way. Remember Penance applies Grace, so if you are helping with tank healing duty keep the Grace stacks solely on the tank.
4. From here you can do 2 things: PoH or FH; you will go with the former if the raid is taking heavy damage, or go with the latter if only one or two in your raid are taking heavy damage.
5. Go back to first priority or redo from fourth priority if the danger is still high, or third priority if your Penance is back.

Seeing this in a spell priority list, it can go like this:

1. PW:S on target taking or about to take damage.
2. PoM on tank or target taking heavy damage if it has WS.
3. Penance if PoM on cooldown. If damage is too high go to next priority.
4. Prayer of Healing if raid damage is too high for your shields (and the other healer's heals) to keep up with.

If the raid is not taking much damage you can chill a little and simply spam PW:S on every raidmate and Penance the tank just to refresh Inspiration.

Each time you cast PW:S you get BT, use this to your advantage for every spell that requires a cast time or channeling. Remember Penance benefits from your BT buff but it doesn't consume it when you cast it, so right after Penance you can use FH or PoH for a very fast heal. Disc (and healer priest generally speaking) has high mobility, make use of it and avoid as much damage as you can.

Something to consider is, for 25 modes, you can remove Penance and PoM from your rotation entirely if the other healers are doing a great job at keeping everyone healthy, if that's the case just PW:S spam on everyone, reapplying PW:S on the tanks as soon as WS debuff is gone as priority.

Tank healing duty (situational)

They want you to tank heal?!? Are they crazy? Are YOU crazy? To be fair the other heal specs may be better at it, but that doesn't mean Disc can't perform. This will happen mostly in a 10mode as having a Holy Paladin in 25mode is extremely important, and Holy paladin will do this job better. If the other healer is a Druid or Shaman you can offer yourself as tank healer. First of all use this talent spec:

• Grace 1/2: Your penance is used on the tank so 1 point is enough, Penance will have 87.5% chance to apply at least one charge per use.
• Renewed Hope 2/2: It gives 2% crit per point to your main heals here, Penance and Greater heal (GH).
• Divine Fury 5/5: Solely for GH.
• Improved Renew 3/3: You will use Renew with this spec so you might as well buff it.

The playstyle changes as well, as you change your mindset from being a PW:S spammer to simply using PW:S to gain Borrowed Time for more effective Penance and GH. So it goes like this:

1. PW:S on tank(s) as soon as WS debuff is gone.
2. Penance always with BT and always have it in cd (Remember Penance doesn't consume BT).
3. Renew on the tank(s), remember instants don't consume your BT.
4. If Penance is in cd and Renew is on the tank, use the last seconds of your BT with a GH.

Things to consider:

• Don't spam your PW:S on everyone; your BT buff will last 4s after GCD from the PW:S is over, then 2.35s from both Penance and Renew, that means you have 1.65s left to use your hasted GH. Once that GH is finished you can PW:S someone to gain BT and start again
• You don't use PoM much with this spec, mostly because there's no reassurance that it will always bounce between the tanks.
• Use Glyph of Renew as your third glyph option.
• If you need BT, you can shield yourself or someone else taking damage, that's perfectly plausible as well, just make sure you use that BT to heal the tank.
• Depending on the encounter, you can incorporate Flash Heal, but generally GH is a safer choice as it benefits more from haste and gives more shield on crit. Another reason is, since Flash Heal heals less, you will inevitably be forced to cast a few of them without BT, making overall heal lower.
• Haste and crit stats gain more value, as you cast less PW:S.
• If you find yourself in trouble, use Power Infusion and GH to your heart's content.

This playstyle is harder due to having more things to keep in mind. You can swap points from Improved Healing if mana is not a concern to something you consider more important.

When to use cooldowns?

Using cooldowns as a healer works in a very similar way as how tanks use theirs. Whenever you think someone is in real danger of dying you might use one of your many cooldowns you have as priest.

• Power Infusion is usually used on a high dps caster, but it can also be used on yourself to power up your long cast time spells. Something often overlooked is the fact that it also reduces costs by 20% so use this to your advantage if your mana is draining fast.
• Pain Suppression is best used on the Tank if damage taken in the next few seconds could cause its death. Usually dps get the blame for getting themselves killed, but if you know the Tank is strong and won't die anytime soon you can choose to save the dps. Needless to say, healers have the next priority after the tank.
• Inner Focus has a long cooldown and it might not seem worth, but have you considered using it with Divine Hymn? A BT buff with Inner Focus can give you a pretty strong and fast to cast Divine Hymn, something the Holy spec can only dream about (not to mention it makes it FREE to cast). If you feel wild you can even Power Infusion yourself to boost the haste on the channel even further. Use this only if a wipe is at risk as it is your best combo.
• Hymn of Hope is best used after you summon your Shadowfiend, when you are at your lowest mana left. The 20% mana increase will allow your little pet to return you absurdly high amounts of mana. To make sure you don't spend an eternity casting this make sure you have a BT buff on you as you cast it.
• Shadowfiend is a pet, therefore it can get buffs like Heroism/Bloodlust when your Shaman in raid uses the ability. As you might guess, the more attacks the pet performs the more mana you get back, so if you know when your Shaman will use the best raid buff available you can also summon your pet a few seconds before.
• Fear Ward lasts 3 min and has 3 min cd, you can just keep yourself buffed all the time without consequences.
• Non critical Desperate Prayer heals about the same as a Critical FH. Use only while moving and if you can't spare a Penance. Remember it can crit and benefit from Divine Aegis.

 Macros

There aren't that many pve macros for priest (at least I don't think there should be a lot). I have so much fun with my hotkeys that I don't use many of them. Even so there are some macros you can use yourself as a starting Disc:

Inner Focus

#showtooltip Divine Hymn
/cast Inner focus
/cast Divine Hymn

This is self explanatory. Your strongest and most expensive spell is the one you must use with Inner Focus.


#showtooltip Power Infusion
/cast [target=name] Power Infusion

This will use PI on any desired target you wish, name can be your name as well if you are feeling wild.

#showtooltip
/castsequence Prayer of Mending, Penance

If you didn't pick talents to lower the cooldown of your Penance, you can use this one to have your PoM and Penance in the same button, since PoM has 10s cd as Disc and Penance has 10s as well if you use the glyph but not the Aspiration talent.

Addons

I don't use any specific addon for Disc priest aside from my UI addon, my action bar addon and my heal/absorbs meter. Regardless of this I recognize OmniCC can be useful to track your Penance and Prayer of Mending spells to know exactly when they will be off cd, in addition to PI and the others of course.

Last thoughts

                 Even tho Disc is a unique heal spec the same rules apply to it as to other healers: Your life>others. keep yourself out of danger so you don't have to waste GCDs healing yourself while others die because you were careless. Remember Disc is a high mobility spec, show your skill by taking the least damage while also keeping everyone's health safe. Disc is so versatile you can be a Tank healer (with the proper spec) if your raid setup requires it. Having played all heal classes at high end raiding I can safely say Disc is the most enjoyable one, at least for me. Give it a shot, you might stick to it over Holy; not to mention Disc can do many things other specs can't do.