Well, they've been developing the game for 10+ years, they've had dozens of patches and PTRs to work from, they're on their 4th expansion, they've had over 10 million subs, and they've earned over 3 billion in revenue.To be fair, WoW isn't hardly the first or worst when it comes to PvP imbalance.
If pvp isn't balanced by now, at what point down the road will it be?
There are players who only care about pvp, and patch after patch is like disappointment on Christmas.