Blue hit it exactly in the lead-in up top. They can't manage the class balance enough to make it work. Since they still prioritize the RMAH, they have to keep the grind, which means overpowered effects (otherwise everyone would get slaughtered). Overpowered effects means little class balance. So when they had to choose between the RMAH and class balance... they shelved PvP in favor of the RMAH.
Screw creating good games; we need to create effective income streams!