Late reply is late but here it goes. Game is going good. Not as cute and casual friendly as someone on this forum seem to believe (curse)
Depends with the meaning of OP, in PvP Hunters, Shadow Priest and Rogues is the way to go if you want an easy time. Many would say mages, how ever I beg to differ since most of their burst is cleansable or dispellable. In PvE warlocks, especially affliction seem to top the meters and blizzard pumping out nerfs to them constantly.
I cant say much about PvE but the new pvp developer seem to be a brilliant man. He is constantly adressing issues and quickly fixing problems. Burst is still to high and way to much cc but they are slowly reducing all of that.
They are also quick to buff classes that are slightly behind. Warriors were imba OP in 5.0-5.1, now they were overnerfed and they are actually buffing them again soon. Which I like since my main is a warrior and right now they are just unplayable. The dmg is decent but dying in a stun from a rogue or mage in the opener is retarded as a heavy wielding armor class. So for now I just capping him with conquest points each week and play on my resto druid