I think there are some post answers about skill before.
The word pretty overpowered for rogue isn't exact enough.
Each class has unique skills itself, can choose "run" or "attack". Even barbarian or bladedancer can run, not always attack or being a tank in arena.
If u know the tactic. U can beat them.
With my good partner, we killed both of them few times. They never won, but i only go arena rarely. Maybe they 'll win of us at next battles.