Here is the thing with a game that is both a PvP game and a PvM game:
When you balance the classes against PvP style of play, you completely upset the balance of PvM style of play.
When you balance the classes for PvM play, you end up with classes that are over-powered due to their role being different in PvP and in PvM.
You are never gonna be able to balance both.
Pick one and balance the game on those lines.
A glaring example of this: Recently damage done in PvP was cut in half, and the result on PvM was that you could only hit human mobs for minimum damage, and doing missions was a nightmare (and still is, since this bug still exists).
or
Agents had Aimed Shot nerfed cause it was doing massive damage in PvP and they were 1 shot killing people. The result in PvM was that Aimed Shot became completely worthless, and Agents had a very very difficult time killing anything since they had no special attack anymore.
Im sure we could all list many more examples of this.
The point is, Over-equipping is mainly a problem in PvP. In PvM the mobs were balanced against over-equipped PCs, leaving the classes who couldnt over-equip a little gimped (or a lot gimped depending on who you talk to). The problem is, people over-equipped originally for PvP, now people have to just to be able to beat a green mob.
Thats why over-equipping needs to be addressed.