This isn't a "problem". It is the nature of an MMORPG. Some people will always try to get the best loot/gear, and as long as there is imbalance, other people will blame those people. But it's not their fault that certain equipment is better than others. And I find it hypocritical and counter-intuitive to blame people for using the equipment that is most effective. It happens in every MMO out there, because it's human nature. Not using the best equipment is akin to being a sadist.
I am almost agree with you regarding human nature and the principle of MMO, instead, i'm not using the best equipment cause i found that using the Black Armor is really masochistic, it's so ugly!
However I hope there is nevertheless some players who do not choose only their equipment because it is OP, but also for style.