There may be a ton of "Warrior OP, nerf!!1" threads however I find it very interesting that mages are flying under the radar at the moment. Great damage, great control (as always) and when played well great survivability as well. Perhaps the reason why is that some would argue mages have a higher "skill-cap?"
Mages are strong, but they aren't overpowered by any means. Honestly, PvP for the most part is actually fairly balanced right now. Only thing I'd change given the chance is put more CC's on DR. Sheep/Fear should share DR, for example. Any 8sec CC should share DR with other 8 sec CCs, 6 sec CCs like Cyclone should share DR with other 6 sec CCs, etc. Other than that, I find PvP to be rather balanced.
Mages are very strong right now, they have just never been easy to play in arenas like warriors are atm. The changes they made to mastery made the skill floor even higher than it was before and if you are not on top of your game as a frost mage you will die in seconds against warrior teams with hunters and enhancements on their side. Because it's not easy to be a good mage, you don't see them that much. When you actually meet a gladiator level mage, they are insanely scary.
Been playing arena on my mage. Even undergeared I do just fine. I learned how to use alter time properly...it can have my babies. Have full procs hitting alter time and unloading everything twice is like magic :P
My only 2 complaints are mastery is boring and not overly useful. And kiting a warriors is like pulling teeth at best of times.