It is as most people have said and as Blizzard has said. They do NOT balance the game around PvP, they balance it around PvE. They try to make adjustments for the PvP game without trying to botch the PvE game. Aside from this, anyone who plays or who has played competitive gaming knows that there is a drastic difference between players at different skill levels; by this I mean that it isn't just the skill level of the players involved, it is also what occurs at the various brackets. What is ridiculous for some at the lower levels, is simple for those at the higher levels; and this is a drastic oversimplification of what is going on, but I assume it is easy to understand where I am going with that thought. So, not only do you have to keep a balance between the PvP game and the PvE game, you must balance DOZENS of compositions at various and different skill levels.
I think a bunch of you are not quite understanding the complexity of the problem. Nothing is as simple as "change this a bit" or "take that out". If you seriously believe that, then you have not thought about the multitude of issues of balancing a game as massive as WoW is and I would implore you all to think about this more before you type.