In my experience it's party composition combined with player knowledge that can be "overpowered".

Two BRDs on both healers together with PLD. Those healers will never cast, forced to pop PvP abilities and after that it's over.

Meanwhile casters and melee are having a field day. xD

SE did a pretty good job with balance in PvP. It's very, very difficult and I think we should praise them for this.

There can be some adjustments of course. xD