I played a Holy Priest from level 10 to 60. I wouldn't mind healing again if I were to do this, but the inefficient farming would be terrible. Having dual spec for Shadow to be able to go out in the world and accomplish something would be nice.
Since I doubt it'll happen, I've also thought about going Mage for DPS or Warrior for DPS/Tanking. As I was able to tank rather efficiently as Fury on my Warrior alt in Vanilla.