I'm Shadanzi author of the Priest blog Power Word: Shadanzi. This was a guide on my blog and I've added a few bits in for the competition and reformatted because that didnt copy over!
Priest Healing cataclysm has really come into it's own. We we're good before the hotfix/mana regen bufff - now we are truly great. The variety of encounters in cataclysm means that priests - always the most versatile of the healing specs - can truly shine. We have a spell for every occasion and every possibility - always ready to react, and to a greater extent than other healing classes, pre-act. A good priest can churn out healing when the going get's tough. A great priest will never need to - everything is expected and precast/prepared for.
First of all - Holy or Discipline?
For many priests right now, this seems to be the big decision. The answer is simple - play the spec you prefer and enjoy more! However I will outline the strength and weaknesses of both in case you would enjoy the most powerful the most.
Strengths - Discipline excels at mitigation and damage reduction, it reigns supreme in encounters with predictable or consistent damage.
Power Word: Shield mitigates damage - quite a lot on the tank with Strength of Soul and Heal - and regenerates mana from Rapture. It also causes Renewed Hope and Weakened Soul for -3% dmg and +10% crit respectively.
+15% Intellect boosts your mana pool, spell-power and crit - very good scaling.
Divine Aegis makes Prayer of Healing (GLYPH IT!) a very potent group heal/shield. If you know group damage is incoming, use it to soften the blow and to top anyone off. No healing should be wasted as people should be kept at 70 - 80%.
Inner Focus gives you big free GHeals on the tank when you need them most - and Train of Thought makes it more efficient to cast occasionally.
Evangelism/Atonement/Archangel may not be the best use of talents, but it has it's uses. I'd skip it but thats a personal thing more than anything.
Penance/Grace make your tank healing abilities pretty strong, giving you bigger Heals on the one who THEORETICALLY needs them most (in practice it's the Rogue or Warlock (UGH)).
Weaknesses - Discipline will never have the raw power of Holy, and can struggle with heavy, random AoE.
Inherently smaller heals mean that without Grace stacks you will need to cast more spells to heal someone up.
While Power Word: Barrier is strong it's just not Guardian Spirit.
Reliant on more expensive Greater Heal and cooldown (Penance) for healing heavy tank damage.
Reliant on crit rating to proc Divine Aegis - current low gear levels can render this talent virtually useless.
Weaker AoE healing even with Divine Aegis on Prayer of Healing meaning you will need more Prayers to get everyone up after AoE - costing a lot of mana.
Strengths - Holy is all about pure, raw, healing power. Versatility is the name of the game with Holy, you can adapt to any situation - and excel at it.
A very potent and scalable mastery. Can easily reach 20 - 30% additional healing with current gear levels - making every heal more efficient.
+15% Healing means you're spells are inherently stronger. Not quite the scaling of Discipline but makes you more efficient with bigger heals.
+40% regen from spirit is uttterly amazing and means you can get truly absurd amounts of mana regen.
Prayer of Healing (GLYPH IT!) and Circle of Healing make for extreme AoE healing. Using CoH then PoH will heal the group for significant amounts and can trivialise most AoE damage. Heavy AoE fight? Pop Chakra: Sanctuary, cast Holy Word: Sanctuary, CoH then PoH and it won't seem so bad.
Powerful, efficient tank healing from Chakra: Serenity. Extra crit on your single target spells and they renew the rather expensive Renew. The Holy Word is very cheap and a moderate amount - and don't underestimate the buff. Holy Word: Serenity, Flash Heal then Greater Heal is a HUGE heal-spike which will save your tank from almost any situation.
Guardian Spirit - enough said.
Body and Soul makes kiting a dream and means you can get in range fast if the tank is knocked back or moves too far.
Test of Faith means you're even more potent when you need it most.
Serendipity makes Flash Heal and Binding Heal much more efficient and means PoH and GHeal are faster and cheaper.
Under used for it's poor scaling- but AWESOME at current gearing levels, Surge of Light gives you free Flash Heals and Serendipity procs.
Weaknesses - Holy is expensive and requires virtually perfect execution - picking the wrong Chakra or healing spell can cause a wipe due to lack of mana or throughput.
Slow heals can be a killer - the lack of Borrowed Time can hurt.
Lower mitigation than Discipline forces you to heal more.
Requires virtually every green number to be effective to be efficient and not to go OOM.
Reliant on mana cooldowns and spirit over more reliable Rapture.
Overall it's a very personal choice. Priest Healing is a strict but potent mistress, learn to love it. Pick a spec and fly with it. Play what you enjoy. Ultimately you're a Priest, you could even heal as Shadow. Healing is what we do.
Now you have a spec, lets look at our targets;
The TANK - The person taking the most damage (hopefully) is going to need the most healing. I see people spamming Heal, Nourish, Healing Wave, Holy Light on the Tank and wondering why he dies. The answer is throughput. As a Priest, Renew the tank as he pulls. Then Activate Chakra/cast Power Word: Shield and cast Heal on him. Use PoM on the tank on cooldown, as well as Holy Word: Serenity/Penance if the tank is at 70% or lower HP. Most of the time you WILL be using Heal. Sometimes the tank will get low. Flash Heal/Power Word:Shield (if he has weakened soul then Flash Heal) him, then cast a hasted Greater Heal (from Serendipity/Borrowed Time) then cast your cooldown (Holy Word: Serenity/Penance). Repeat if necessary. Sometimes I even FHFHGH as holy for huge, fast throughput. (It's hard on mana but I've got about 3-4k mana regen in combat with procs up (and I always seem to have one proc up)).
The HEALER (YOU) - You matter most after the tank. Some healers forget to heal themselves. It sounds elementary, but Binding Heal is your friend. Renew yourself and use Power Word: Shield, then pop a binding heal on someone else who's low and get back to healing other people. It even procs serendipity for a quick PoH or GH.
The DPS - They need to be alive to kill things. I've seen a lot of healers Heal (or equivalent) spam the tank and let DPS die from unavoidable, slow, aoe damage. It makes me sad. As Priests we are powerful and versatile multi-target healers. You can point heal in Chakra: Serenity with Heal and the odd Flash Heal/Greater Heal, use Binding Heal and Flash Heal to get quick, cheap PoH's, just simply cast PoH a few times, spread renew and Shields around and use CoH, or even use Chakra: Sanctuary. You can heal the DPS. I don't go oom from keeping everyone alive with a variety of spells, and because the DPS are up and DPSing things die faster, so I don't have time to go oom.
So lets look at our Healing Priorities: (This list assumes you PoM the tank on CD, and maintain renew on the Tank.)
Tank < 25% - Flash Heal/Power Word: Shield + Holy Word: Serentity/Penance + (Inner Focus) Greater Heal - If whole group is low use Divine Hymn/Prayer of Healing.
Healer < 40% - Renew + Shield (sometimes as Holy too for running away form Bad) + Binding Heal (most likely on the Tank)
DPS < 40% - Renew + Binding Heal or Heal - If multiple party memebers are low (3+) then Prayer of Healing/CoH
Tank < 60% - Holy Word: Serenity/Penance + Heal
Dispel important Debuffs
Healer < 80% - Renew + Binding Heal
DPS < 80% - Renew - Point out there is a Lightwell
Tank < 80% - Heal or Holy Word: Serenity/Penance if available for efficiencies sake
Regenerate Mana! - If at any point you reach 25% mana use Shadowfiend UNLESS all group members have about 70+ % hp, then use Hymn of Hope.
Another important issue is mana regen. Make sure 80+ % of your gear is Spirit Gear and reforge the other pieces to spirit. If you have too much spirit it's easier to reforge down than hunt gear to get more. Get as much mastery/spirit gear as possible - mastery is amazing! I currently have an average of 4k combat regen with procs (Blood of Isiset, Tear of Blood, and Heartsong are VERY helpful) and about +25% healing as Holy. The +25% HoT is amazing, especially for DPS - and makes PoH pretty huge - and ever so efficient.
Healing in Depth
DISCIPLINE in Depth.
Pre-shield the tank, go back to basics. When Shield drops PoM and renew. And basically chain cast Heal, PW:S-ing whenever you can (Strength of Soul is your friend)
If DPS take damage renew and PW:S them.
If theres sudden aoe, PW:S youself and cast PoH under Borrowed Time, then point heal with heal.
Should someone be getting low, shield and Greater Heal them, preferably under Inner Focus.
When healing the tank gets tough, and it will... a lot, then try and use the following priorities: PW:S, PoM, Renew, Heal >50%, Greater Heal then Penance 25-50%, Flash Heal then Penance <25%. That normally works, granted your mana will dissolve if you have to do it too much, but that normally means the tank need some better gear.
That covers most of the bases with discipline. The only other thing is the good old Atonement/Archangel debate. My advice would be to avoid it until you're comfortable, THEN consider it. It can be nice because it will keep the tank up, and the +15% helps in aoe phases and tank heavy phases, but is by no means necessary. The mana is nice, but negligible, it costs more to smite x5 and pop AA than not to until we have a bigger mana pool. And that is, in essence, the basics of Discipline as I see them right now.
HOLY in Depth
Before the pull put PoM and renew on the tank. Drink for a second (Mage cakes ftw) and the hit Chakra. If you know the boss fight, chances are you know if you need to be in Chakra: Serenity or Chakra:Sanctuary. Almost every time you're going to want Serenity. The instant, cheap, big heal is nice, and the buff for 25% crit is a real life saver sometimes on the tank. Occasionally half way through you may need to switch to sanctuary, but it's often unnecessary, though useful.
If DPS take damage, throw renew (and maybe a Heal) on them and point out theres a lightwell for them to use.
If you take damage renew yourself, click your lightwell, and if needs be, Binding Heal. I LOVE Binding Heal. It procs serenity too, which makes for some fast and cheap PoHs/GHs
If there is heavy AoE, then FH the lowest target, BH the tank, cast PoH under 2x Serendipity and CoH. If that's no enough, rinse and repeat or consider changing to Sanctuary. People stand in bright light most of the time... even if it is fire.
If someone gets dangerously low, Flash Heal. The 12% healing buff from Test of Faith means it isn't the waste of mana you might think. If the Tank gets dagerously low, then HW: Serenity and the FH them. PoM and Renew should be on them/on CD already.
And remember Guardian Spirit. If the tanks about to die, use it.
Should everything go wrong hit Chakra if it's off CD and PoM the tank then hit Divine Hymn. If Chakra is on CD then push Divine Hymn anyway. It's like god mode.
And that is the basics of Holy. There are nuances and clever switchings of stance (Chakra and Inner Will/Fire) unmentioned because they are very situational. Use Inner Will until you have the mental haste (IRL and GCD wise) to switch to Inner Fire for your PoH's, GH's and Heals. Remember Shadowfiend and Hymn of Hope. Beyond that good luck and get good trinkets. I find +Int with a Spirit proc far better than +Spirit with a random proc. Every piece of gear should be spirit gear. If you get a good drop without spirit, then reforge it. Spirit gear is easier to reforge to other stats when you have enough spirit than the other way round, and right now, you want LOADS of spirit.
Discipline is all about balance - most of the time!
Intellect is your number one stat, no surprises there. With the recent Rapture buff and the Enlightenment Tree bonus Discipline essentially sees the highest Intellect scaling of all.
Spirit is second to Intellect for Discipline mana regen - however it is still a very important stat.
As for crit, haste, and mastery they all scale better the more of them you have. It's good to keep them balanced for discipline right now because you cannot realistically reach any sort of 'cap' without massively gimping the other two stats. Crit gives you more DA procs. Mastery bigger shields (though scales with DA poorly). Haste gives you faster GCDs, Renews and Casts. Haste makes Strength of Soul better, which means more PW:Ss which means Mastery scales better, and you're casting more spells, so crits occur more often. There is a lot of variation on the prioritization for discipline - it's highly dependent on role, however balancing them (maybe biasing haste and mastery) is the strongest overall in my opinion.
Holy is where you start to see a real split in thinking and direction.
Intellect and Spirit are top. They both need to be high (Intellect will be higher naturally - but relatively they will both be high). I gem red and blue slots with Int/Spirit gems. More int and spirit means bigger spells, and more longevity - evermore important in Cataclysm.
Beyond this you want to avoid crit. It's not that strong because we can get +35% crit when we need it. It's nice to have some, but it's not something to stack. I mention what to avoid because I'm scared to mention haste and mastery.
Haste vs Mastery is the subject of many Holy Priest debates. Haste is strong because you can cast faster and more often - getting off more spells. However, with enough spirit it becomes more and more unnecessary as you can afford to cast Flash Heal when you NEED speed. Mastery is the opposite - to have high mastery your going to have less haste. You will cast slower and less often - but your spells will be HUGE. I get 2-3k Echo ticks on the tank from GHeal which makes tank healing much less mundane and Heal spammy. It also makes you efficient - haste makes you less efficient as you burn mana faster. Mastery means your HPM increases dramatically on all spells (Renew to a much lesser extent) and means expensive spells like Prayer of Healing become efficient AoE Heal-Nukes. I favor mastery, some favor haste. I raid heal so Mastery is hands down win IN MY OPINION. It's a style thing. It's personal, so do what you feel best and don't yell at me for liking Echo!
Good luck in the great new world of Cataclysm. It will both challenge and test you but it's worth it - it's making you a better Priest. I've started raiding (with a horrible Drake comp on Halfus) and completed most of the Heroics. It's tough at first, but it gets better as you get into the right mind set - the right Chakra if you will. I hope you found my guide useful and hope you will get in touch for any clarification at Power Word: Shadanzi.