I know I have been reviewing Holy Talents, but I wanted to insert a post on the Disc talent Grace. This talent is designed to increase our single-target healing capability, without giving us all the permanent +healing modifiers that Holy has.
The way it works is a little clumsy, and Blizzard has admitted they feel it's an awkward mechanic. But it does serve to increase our tank healing by 9% for just two talent points. (Or one point, if you don't mind the stack dropping occasionally due to the RNG). This is a big boost... of course with the caveat that if you heal anyone else, you'll lose the bonus until you cast a few more heals.
Or will you? The Grace stack is only refreshed (and moved to a new target if applicable) on casting a direct heal. That is, Flash, Greater, or Penance. It's not refreshed by shields, HoTs, or group heals. This means we are free to cast PW:Shield, Renew, Prayer of Healing, Prayer of Mending, and even Binding Heal on anyone we like without losing our Grace stack. This is a surprising amount of versatility given the initial impression of the talent's limitations.
Penance and Shield are a disc priest's meat and potatoes. Given that Grace works the way it does, Penance can be cast on a tank on cooldown, and Shield can be used on the tank every 15 seconds and on anyone else whenever else you like, while still maximizing Grace usage. Furthermore, a Prayer of Mending can be launched off every 10 seconds or so, bouncing across the raid (and creating little Divine Aegis shields too) without affecting the Grace stack, yet still benefiting from it when it bounces back to the tank.
Using this technique, you can heal multiple people while still getting full use out of Grace on your main ward. You can reserve Penance (and Flash in some cases) for the MT, but also help out an OT by keeping them shielded (with Glyph!) and Renew'd. If the OT needs a direct heal, you can even cast Binding Heal (which is as powerful and fast as Flash) without losing Grace on the MT.
Now, all of this advice is only relevant for some fights. In any easy fight, you probably won't need Grace, so you can Penance anyone who's low. And certainly in a hard fight, keeping your tank up takes priority to throwing out heals (especially expensive ones like Binding) to others. But I feel it's good to know how to finesse Grace, to keep up its bonus, while still healing someone who needs it in an emergency. A 9% bonus on one person may seem like a drop in the bucket, but we've all had times where a tank had 500 health for a few perilous seconds, and next time it might just be the bonus from Grace that gave him or her those 500 hit points to begin with.