they've readily stated that PvP in general won't be as balanced as PvE simply because of the amount of builds and because its not the main focus of the game.
Blizz has stated the D3 is a PvE focused game, however it's also been said that they may hold PvP tournaments (similar to WoW arena tournaments). This alone tells me that Blizz plans for PvP to be balanced as well, at least 3v3.