I did this a while ago for the Druid so here we go again for the Priest. As before, this is primarily on changes that affect healing Priests and the changes are taken directly from the patch notes. If there are any undocumented changes, please let me know.
Warning: This post is EXTREMELY long. Consider yourself warned.
Blue Comments are for PvE
Red Comments are for PvP
Green Comments are for both PvE and PvP
Mana Regeneration: The amount of mana regeneration derived from intellect and spirit has been reduced by 40%; however, talents that allow for mana regeneration while in combat have been increased. As a result, in-combat regeneration for classes with those talents will stay the same, while out-of-combat regeneration will be lower.
PvE: Nerf. Sneaking in Oo5SR mana regen through crafty usage of clear casting, stop casting and Inner Focus was a skill, however, as you usually can’t get out of combat in a raid boss fight, more concern will be given to managing mana than pre 3.1.
PvP: Negligible. If you’re a healer and your out of combat, you’re drinking.
Abolish Disease: Now cleanses a disease every 3 seconds, down from 5. Duration reduced from 20 seconds down to 12 seconds.
PvE: Buff. Having to wait 5 seconds to dispel a disease sucks, especially if you’re pre-abolishing an anticipated disease a la Heigan from Naxx. 3 second ticks are much better
PvP: Buff. Same deal, especially if you’re fighting a DK with dispel resistance.
Devouring Plague: This spell now has a new icon.
Icon looks 10x more badass.
Divine Hymn: Redesigned: You recite a Holy hymn, summoning the power of the Divine to assist you in your time of need. Heals 3 nearby lowest-health friendly party or raid targets for 4960-5208 every 2 seconds for 8 seconds, and increases healing done to them by 15% for 8 seconds. Maximum of 12 heals. The Priest must channel to maintain the spell. Cooldown increased to 6 minutes, up from 5.
PvE: Buff. An 8 second channeled smart heal is amazing. Yes, the CD is long, but it can easily make/break a fight gone bad. Keep in mind that you should probably PW: S yourself to prevent pushback, and if you’re deep Disc specced, to proc Borrowed Time, thus shortening the channel.
PvP: Nerf. Divine Hymn as an incapacitate was amazing when dealing with fear immune opponents or opponents that were Mana Burn-able as it didn’t immediately break on damage like Gouge or Sap. It was pretty much the only ability guaranteed to allow one to get distance on a Feral Druid during Berserk.
Divine Spirit: Now trainable at level 31.
Thank you, Blizzard.
Holy Nova: Mana cost reduced approximately 20%
PvE: Negligible. It’s still party only and relatively weak when compared to the new Prayer of Healing, and as such, usually not a go to spell for raids.
PvP: Buff: Mostly used to pull stealthed classes out or as a spammable self heal while getting trained. 20% reduction in cost is a step in the right direction.
Improved Holy Concentration: Removed
PvE: Negligible: Incredibly fast Greater Heals were nice, and thankfully, they’ve been rolled into Serendipity, only now, they’re controllable instead of completely random.
PvP: Negligible: Who specced deep Holy for serious PvP?
Hymn of Hope: Redesigned: You recite a Holy hymn, restoring hope fto those in despair. Restores 3% mana to 3 nearby low mana friendly party or raid targets every 2 seconds for 8 seconds, and temporarily increases their total maximum mana by 20% for 8 seconds. After the effect expires, the mana is lost. Maximum of 12 mana restorations. The Priest must channel to maintain the spell. Cooldown increased to 6 minutes, up from 5.
PvE and PvP: Buff… sorta: The old Hymn of Hope was pretty bad because the amount of mana regenerated was terrible, topping out at a few thousand mana, to only the Priest and their party. This new version is much better in that it’s ‘smart’, through its automatic selection of nearby raid members who have low mana, however, after the total max mana buff ends, you lose the bonus mana and you’re left with the same crappy mana return that you would have gotten from the old Hymn of Hope. The best way to utilize this would be to bomb heals as fast as possible to uze up the bonus mana before you’re relegated to OOM status again. In addition, those players that you affect with HoH should also recognize the bonus mana and start nuking hard, spending the additional mana before they lose it. It could be feasible for several Arcane Mages and several Priests (Shadow or Healing) to stand together and chain HoH and nukes… hrm…
Psychic Horror: Now affected by Mental Agility, Inner Focus, Shadow Reach, Shadow Focus, and Shadow Affinity
Prayer of Healing: This spell now heals the target's party, rather than being limited to just your direct party.
PvE: Buff: This is now a huge, cooldown-less, version of the old (early TBC) Circle of Healing. It’s still limited by party mechanics but as long as parties are created semi-intelligently, it can definitely help with AoE healing.
PvP: Negligible. Who casts PoH in PvP?
Shadowfiend: Health scaling increased. Now receives 30% of the master's spellpower. Mana return increased to 5%, up from 4%. The Shadowfiend now returns mana when its melee attacks land, rather than when it deals damage. No longer has a 75% reduced chance to be hit by m3lee, ranged and spells. Movement speed normalized to player movement speeds. Tooltip revised. New Shadowfiend ability, Shadowcrawl, teleports the Shadowfiend to an enemy target and increases its damage done by 15% for 5 seconds.
PvE: Semi-Nerf: The removal of the 75% avoidance really hurts the Shadowfiend as it pretty much dies to anything and everything. Great, it has more HP, but if a boss uses an AoE attack, it’s pretty much toast anyways. If you’re fighting a boss that doesn’t have AoE’s or random splash damage, then the increase in man a return is very helpful, so that aspect could be considered a minor buff.
PvP: Nerf. The loss of avoidance means that the Shadowfiend is incredibly crowd controllable. Snare it, root it, fear it, whatever. Great, it gives mana back on hit instead of damage, but how can it hit anything when it’s affected by every debuff in the game?
Divine Aegis: Divine Aegis effects will now stack, however the amount absorbed cannot exceed 125*level (of the target). It will also now take into account total healing includeing overhealing.
PvE and PvP: Buff: Stacking DA is huge. A level 80 can get a maximum stack of 10,000 damage absorbed through DA alone. I can imagine why Rapture was nerfed to no longer work on DA procs. With the de-cluttering of the Disc tree and overall increase to survivability, more PvP Disc’s will be able to take DA instead of committing points on efficiency talents. There are initial reports of 'rolling' DA's where additional DA procs become additive across multiple Disc Priests. If this is true, then we have a very powerful scaling mechanic.
Improved Divine Spirit: This talent has been removed
Improved Flash Heal: New Talent: Reduces the mana cost of your Flash Heal by 5/10/15% and increases the critical effect chance of your Flash Heal by 4/7/10% on friendly targets at or below 50% health.
PvE and PvP: Buff: This talent, combined with the Glyph of Flash Heal makes Flash Heal incredibly efficient and a very quick 'save me' ability when Penance is down. PvE Disc Priests will likely have very high crit rates and an extra 10% crit will go a long way towards Divine Aegis procs.
Grace: This talent no longer decreases damage done to the target, but the duration has increased to 15 seconds and the healing bonus has increased from 2% to 3%. This effect now cannot be applied to more than 1 target at a time.
PvE and PvP: Nerf: The damage reduction ability was quite nice, and its sad to see it go, especially since a single Penance could apply a 3 stack very quickly. The healing bonus buff was rather nice, but now that it can't be applied to multiple targets, Disc Priests shouldn't count on it staying on their primary target.
Improved Power Word: Fortitude: Now also increases your total stamina by 2/4%
PvE and PvP: Negligible: While a bit more stam is always nice, only 1 Priest in the raid needs this talent. The 2 talent points needed to fill this talent is most likely better allocated elsewhere for both PvE and PvP.
Meditation and Improved Power Word: Shield: Have changed locations with each other.
Meditation: Now grants 17/33/50% of mana regeneration while casting.
PvE and PvP: Negligible: This, combined with the overall nerf to mana regen ensures that the in combat regen stays the same.
Mental Agility: Reduced to 3 points (4/7/10%), down from 5.
PvE and PvP: Buff: Bloat reduction is always good
Soul Warding: New Talent: Reduces the cooldown of your Power Word: Shield ability by 4 seconds, and reduces the mana cost of your Power Word: Shield by 30%.
PvE and PvP: Buff: Cheap shields and quick cooldown means that Power Word: Shield can be passed out like candy. This is also likely the other reason why Rapture got nerfed to hell.
Penance: Damage increased approximately 30%. This spell can now be cast on yourself.
PvE and PvP: Buff: The fact that it is now selfcast is huge. Quick self healing for a huge amount allows for the Priest to get back to healing other targets as fast as possible. The damage buff is very nice as well for PvP'ers after a Holy Fire/Smite/Mindblast chain. Keep in mind that since Penance is channeled, it benefits from Borrowed Time, but doesn't consume it.
Power Infusion: This effect now has a new spell effect.
Renewed Hope: This talent also now allows you to proc the Renewed Hope buff on all party/raid members every time you cast Power Word: Shield, reducing damage taken by 3%. Lasts 20 seconds.
PvE and PvP: Buff: It's a pretty minor buff, but it encourages players to use PW: S alot more than people have been using it.
Unbreakable Will: Increased from 3/6/9/12/15% to 6/12/18/24/30%
PvE: Negligible. CC's in PvE? Right.
PvP: Huge Buff: This stacks with stun reduction metas for nearly half duration stuns, silences and fears.
Body and Soul: New Talent: 2–point talent. When you cast Power Word: Shield, you increase the targets movement speed by 30/60% for 4 seconds and you have a 50/100% chance when you cast Abolish Disease on yourself to also cleanse 1 poison effect in addition to diseases.
PvE: Negligible: There's rarely a need to self cleanse a poison in PvE and the movement speed increase, while nice, isn't necessary to fight bosses.
PvP: Buff: This talent opens up the Holy tree for some interesting specs that allow for faster movement and more burst damage from Searing Light. Flag carrying in WSG was never more enjoyable.
Circle of Healing: Healing increased by approximately 40%
PvE and PvP: Buff: 40% more ez healz? Okay!
Holy Concentration: Redesigned: Mana regeneration is increased by 16/32/50% for 8 seconds after you critically heal with Flash Heal, Greater heal, Binding Heal or Renew.
PvE: Nerf: Free heals could be abused to stay oo5SR. This talent will never regenerate as much mana as a free Greater Heal. It could be said that the increased mana regen could be very frequent if the Priest uses alot of casted heals, however, healing as a Holy Priest ends up being very instant dominated unless someone is about to die.
PvP: Nerf: PvP gear has less spirit on it than PvE gear, thus rendering this talent even less attractive.
Empowered Renew: New Talent: Your Renew spell gains an additional 5/10/15% of your bonus healing effects, and your Renew will instantly heal the target for 5/10/15% of the total periodic effect.
PvE and PvP: Buff: Somewhat like a reverse Lifebloom, this new talent allows Holy Priests to compete somewhat with other raid healers when Circle of Healing is down and a bunch of people need a small heal to top them off. With the nerf to Plague Strike, a super strong heal over time is very nice for PvP.
Serendipity: Redesigned: When you heal with Binding Heal or Flash Heal, the cast time of your next Greater heal or Prayer of Healing spell is reduced by 4//8/12%. Stacks up to 3 times. Lasts 20 seconds.
PvE: Buff: Casted spells aren't frequent go to spells for a Holy Priest unless someone is about to die. In this case, being able to bomb a superfast Greater Heal is very nice for when it's needed.
PvP: Buff: Holy PvP Priests cast alot of Flash Heals, which can help them keep teammates up with big Greater Heals.
Test of Faith: No longer increases critical effect chance of your heals, but healing done on targets lower than 50% is increased from 2/4/6% to 4/8/12%.
PvE: Nerf: The value of crit increases when someone's in danger of dying, especially if it can proc instant Flash Heals from Surge of Light and Holy Concentration.
PvP: It's unlikely that anyone would get this talent as it is very situational, but the loss of crit does hurt the efficiency of an already inefficient spec.
Glyph of Penance: Reduces the cooldown of Penance by 2 seconds.
PvE and PvP: Buff: Amazing glyph. With the nerf to Rapture, getting more mileage out of Penance (Disc Priest's most efficient heal) is absolutely needed.
Glyph of Guardian Spirit: If your Guardian Spirit lasts its entire duration without being triggered, the cooldown is reset to 1 min.
PvE and PvP: Amazing glyph. A 1 minute cooldown is amazing when one considers the 40% bonus healing effect allows healers to redirect their attention elsewhere. This ability also greatly improves a Holy Priest's efficiency as they won't have to heal as much to do the same amount of work.
Glyph of Pain Suppression: Allows Pain Suppression to be cast while stunned.
PvE: Negligible: When do players get stunned for any substantial amount of time in PvE?
PvP: Negligible: With 30% stun duration reduction and pre-buffing, a Priest shouldn't need to expect to be stunned that much that they have to get this glyph.
Glyph of Hymn of Hope: Your Hymn of Hope lasts an additional 2 seconds.
PvE and PvP: An extra 3% mana? For a Major Glyph? On an ability with a 6 min cooldown? No thanks.