Rogues obviously, followed extremely closely by mages. It's a repeating pattern to have rogues and mages dominating expansions but in this expansion rogues have REALLY outdone themselves.
GC himself recently admitted "rogues are the best designed class" - meaning that every other class simply isn't equipped as well as rogues when it comes to having so many offensive and defensive tools at their disposal.
Recuperate coupled with the huge vanish buff (i.e. they get to vanish no matter how terrible they are) has literally doubled their survivabilty, and survivability used to be a rogue's greatest weakness once upon a time. Catching one in the open meant hell for the rogue, but they compensated by being able to lock you down while bursting. But now rogues have lost very little of their control (kidney shot nerf) while having gained ridiculous amounts of survivability. They vanish with 5% health remaining and the next time they re-open on you they're back at 50-60%. Rogues have always had the option to buy time for their cooldowns, but atleast you could be sure that they had no way of healing it back - except now they CAN heal back, and huge amounts at a time.
I miss the days when getting a rogue to low health actually meant something, I miss the days when rogues were viable kill targets in arena. In their current state it's foolish to try and focus a rogue.
But hey, I can't say much since I'm a mage, who is almost just as overpowered ;)
I would have to say I agree 100% with this. Ret Paladins aren't even anywhere close they are one of my easiest fights (if not the easiest) as an Enhancement Shaman.