This is it -- the last priest healing boss guide of the expansion! (After this, it's pandas or bust, baby!) Are you excited? You should be, because the last boss fight of Cataclysm is
Priests of either spec should know that cooldown management is the key to succeeding in this encounter as a priest. The encounter as a whole is not particularly difficult, but using your regen cooldowns at the right time will pave the way for you to hold onto just enough mana from start to finish. I recommend using your first Shadowfiend after the Mutated Corruption dies on the first platform, and your first Hymn of Hope just after jumping over to the second platform. Your second Shadowfiend should be used as soon as it becomes available, which will allow you to pair your third Shadowfiend and second Hymn of Hope together (just like we used to always do it in Wrath -- cast Shadowfiend, then immediately follow it up with Hymn of Hope). From there, use everything on cooldown, and you should be sitting pretty for mana the whole fight.
In phase 2, you'll be raid healing again, this time against the damage done by Shrapnel and Corrupted Blood. Holy Word: Sanctuary is now plenty effective, since your raid is stacked up the whole time. You can use Divine Hymn again this phase, though save it until the Deathwing gets to 10% or 5% health when Corrupted Blood gets stronger (you'll want to have a cooldown rotation to keep things in order, as always). Guardian Spirit will be reserved for your tanks when the Elementium Terrors come up.
Discipline strategies Most of your time will be spent pre-shielding players with Power Word: Shield on this fight. In phase 1, you'll want to target players with low health so they're not killed by the Mutated Corruption when it crashes against the platform. In phase 2, shield players who get the Shrapnel debuff so when the damage hits, a good chunk of it is soaked by the shield.
Cooldowns like Power Word: Barrier can be used in phase 1 against the Elemental Bolt damage with some attention to placement. You want to place it away from the impact point of the bolt so you're not mitigating damage your raid could have otherwise avoided from being farther away. It's best to place the barrier on a marked player so the raid knows where to stack up ahead of time.
In phase 2, the raid will be stacked up, so barrier placement is a given. Just make sure you're saving it for when the damage from Blood Corruption is actually difficult to manage. Pain Suppression usage is the same as it is for holy; in phase 1, use it on the tanks against Impale, in phase 2, also on the tanks but when adds are up.
Heroic Dragon Soul
The following are some notes and insights I have about healing heroic Dragon Soul so far. If you're a strict holy priest, you probably won't like what you read, but do take things into consideration. Holy's lack of a real raid cooldown has hurt its viability in cutting-edge heroic content tremendously this expansion, and I wouldn't expect to see many holy priests making it into the later encounters of heroic Dragon Soul until the content is nerfed or gear is stacked enough that the fights become easier.
Morchok Because the heroic mode of this encounter is pretty much the same fight, there isn't much more for a priest to know. Neither spec is favored.
Warlord Zon'ozz Both specs are good for heroic Zon'ozz, for different reasons. Holy has more mobility (the core spells in their tool box are mostly instant-cast) to keep up with the increased movement in the fight, while disc priests benefit from being able to pre-shield targets during the black slime phases.
Yor'sahj the Unsleeping In general, priests are strong on Yor'sahj because of Prayer of Healing and Prayer of Mending. AoE and smart healing spells don't give you much control over who you're healing, so you're always at risk of accidentally stacking the Deep Corruption debuff on the wrong target if you use Circle of Healing or Wild Growth. With Prayer of Healing, you know exactly who you're healing, which makes a big difference on the more stressful heroic mode of this fight. Prayer of Mending, on the other hand, is a free heal to spam on cooldown, since it doesn't apply a stack of Deep Corruption at all.
Beyond that, both specs can be used on heroic Yor'sahj. Holy priests are useful for blue slime phases because they can drop Lightwell and Holy Word: Sanctuary before losing all their mana. Disc priests are obviously good because of Power Word: Barrier, provided you're not on a purple slime phase.
Hagara the Stormbinder From what I understand, most raids are choosing to brute force the healing on this fight by letting some or all of their healers stand in the middle, taking damage from Watery Entrenchment and healing through it. In that case, both specs fare all right, with holy being strongest for its ridiculous amounts of HPS, and disc for Power Word: Barrier.
Ultraxion You will probably want to go disc on this fight just because it's a DPS check. You simply don't need all the healers you bring to the fight for the first 4 minutes, so having Atonement and Power Infusion are an added bonus holy can't bring. On top of that, Power Word: Shield, Pain Suppression, and Power Word: Barrier are all ideal tools for dealing with Hour of Twilight.
Warmaster Blackhorn Disc is also stronger than holy on this encounter because of the damage in phase 2. To survive the increasing damage from Disrupting Roar, it's essential that you have as many damage-mitigating raid cooldowns as possible. Divine Hymn does nothing if people are getting one-shot. Barrier is also good for the Twilight Onslaught in phase 1, provided they're back up for phase 2.
Spine of Deathwing Both specs are arguably good on this fight, though it's a little hard to tell at this point if holy is on equal footing with disc. Disc's cooldowns and utility is what will bring it to the fight, but it's also excellent for its ability to quickly swap between dispelling the Blood Corruption debuffs (Blood Corruption: Death and Blood Corruption: Earth), healing the tanks, and shielding the players with Fiery Grip.
Madness of Deathwing I can't really say anything about this encounter at this time, unfortunately. I'll come back later and update this when I've got more than just speculation.
- Priest healing for Morchok, Warlord Zon'ozz, and Yor'sahj the Unsleeping: Healing priest strategies for Dragon Soul's first three bosses
- Priest healing for Hagara the Stormbinder or Ultraxion: Priest healing for Dragon Soul's Hagara and Ultraxion
- Priest healing for Warmaster Blackhorn and Spine of Deathwing: Healing priest strategies for Warmaster Blackhorn and Spine of Deathwing
Spiritual Guidance has the inside line on healing priests in patch 4.3. Check out the 4.3 raid gear guide to plan your next upgrade, or leveling a healing priest if you're just getting started.