Pinot, heres what i think: blizzard didnt gave a f*** for PvP balance before the x-pack release. Things were tuned for PvE content, and u can clearly see that on DK's habilities, a class that relies on dmg supression, such as anti magic shield, and bone shield, designed for PvE tanking. Now they use them in PvP ofc, and the result is unbalance.
Retri paladin were a joke for years. My main was a paladin, 170 days played on him and 80% i was a healer. Now they output more burst dmg then ever, and theres millions of paladins walking around.
Mages are Blizzard's favorite class. I mean, mages get everything they want, u just have to request it, so its not a shock that they pom pyro for 20k atm.
What about rogues? not only they can take 80% of my health with 2 backstabs, now, they can even aoe.

this has all to do with custumer happiness. most ppl, myself included, has a mage, a rogue or a paladin alt. DK is the new attraction, so thats one more reason for them to be...OP.
so why not release a x-pack that suites +50% of the playerbase?

I have a stong belief that PvP will get balanced. Problem with wow is that PvE always get served first, so u gotta live with it.

Anyways, i've been running AV with my 5, and i really cant comlpain that much, im still having fun.
Things are getting nerfed already in this next patch. And in some time, either we get buffed, or more nerfs will be applied.