Depending on work (RL) I will be running my priest team in Cata. I created a couple videos of the team at level 75 (search YouTube for Owltoid to see the 2 videos) and they were doing well. With the Cata changes, I envision 5x shadow priests who use holy nova to heal (stay out of shadowform when the pressure is on). The ability to spam SW: Death at a target below 25% is probably the best execute in the game. Plus it will generate all that mana you lost, and a wave of holy novas heals all your toons just fine.