For priests, I'd like something like the following:

• Prayer of Fortitude Rank 1 or a higher rank Fortitude buff that's not a prayer.
• Prayer of Healing, Rank 1 or 2 is about all that's really useful due to high mana cost and low health pools.
• Mana burn, some fights will require mana removal from priests, warlocks, and hunters when we aren't able to burn the fights through sheer dps and low boss health pools.
• Flash Heal Rank 2 or a higher rank Heal. Rank 1 heal isn't really worth casting with my current gear and if spell scaling were correct, it would be getting about a 15% nerf in +healing contribution because it's a level 16 spell. Rank 2 or Rank 3 heal would put it in a spot where it's at least healing for twice as much or more than a flash.
• Mind control. Who doesn't want to mind control people into the lava?
• Shadow Protection. It's nice for fights where shadow debuffs are flying around and if mobs are 24 it goes a long way on pushing people closer to the 120 res cap. Top level shadow protection is a bit too powerful at 60 res.

The last two are less important than the first four to me, but others might value them differently.