Over the next several days, I will be addressing different pieces of the incoming 3.2 patch that is now on PTR. I could try to make one post about it all, but it would be very very long, and I really *am* trying to keep my posts from going on for like, ever.
Therefore, I'm going to start by pulling out general changes that will affect mana regen, and also changes for holy/disc priests (mainly because there are very few). Even though 3.2 is only on PTR and will likely undergo plenty of tweaking, in general the issues themselves still are subject to developer manipulation, though the exact numbers, and sometimes timing, may vary. Please note that I do reference a lot to the WoW fora (anal retentive Latin major here, folks. If you ever want to know why it's "fora" and not "forums" just let me know, mwahaha). This isn't because I particularly enjoy weeding through the massive amounts of cobknobbery that is the WoW forum, but because this is where we get official word from blues.
Replenishment: This buff now grants 1% of the target's maximum mana over 5 seconds instead of 0.25% per second. This applies to all 5 sources of Replenishment (Vampiric Touch, Judgements of the Wise, Hunting Party, Enduring Winter Frostbolts and Soul Leech).
Mana Regeneration: All items that provide "X mana per five seconds" have had the amount of mana they regenerate increased by approximately 25%.
Prayer of Healing: The percentage of spell power this spell gains in healing (per target) has been reduced from 80.7% to 52.6%.
Penance: Cooldown increased to 12 seconds, up from 10 seconds.
Inspiration: The buff from this ability now reduces the physical damage taken by the target by 3/7/10% instead of increasing the target's armor.
So, in general, the idea is that the 20% nerf to replenishment will be offset by the 25% buff to Mp5. In fact, depending on how much you rely on Mp5 and Replenishment, it could be a buff or a nerf. This really depends a lot on what you stack. The way I see it, it's just more proof that spirit is becoming less and less valued. Of the three mana regen components, spirit, intellect, and mp5, I'm finding myself gemming and enchanting much more often for the latter two. The spellpower bonus of spirit is nice for my priest, but I just don't know if it's worth it anymore. Many of the mana "panic mechanics" (such as Hymn of Hope and Shadowfiend) are now based on your mana pool, not on your mana regen stats. I could go on and on about how much I miss the good ol' days of spirit stacking, but I will end it here.
The Penance cooldown change, as well as the inspiration change, both appear to be for pvp reasons. For PvE and raiding, I cannot think of any fight in which you will notice the change in Inspiration. I'm guessing it is intended more to be a buff in response to increase in armor penetration mechanics in PvP. From what I've read, the nerf to Penance appears to be in response to Disc priests being considered a bit OP in PvP. It will be interesting to see how much of a nerf it is for raiding Disc priests.
And now... commence QQ regarding Prayer of Healing. In 3.1 we got two significant changes to this spell. 1) it could now be cast on anyone in the raid, instead of just on our party. 2) the long cast length is greatly reduced by three stacks of Serendipity. It still has a high mana cost, even with the reduction afforded by the Healing Prayers talent, but I lurrrve this spell. It is a staple for powerful raid healing, and is still a strong option for Disc priests, when they need to do some spot AoE healing. I probably overuse it actually. It's not a huge nerf, but I guess the two buffs to it in 3.1 have made it a bit OP, and it was time to reduce some of the spellpower gains. I will try to dry my eyes. I hate to see it nerfed at all though, but maybe it will force me to use it a little less often... and maybe I'll save a little more mana. Still... sad face.