SWTOR - over powered players griefing

As it says in the title. Some classes are over powered, and the class imbalance seems way out of hand that it basically becomes griefing or rather unplayable especially if its a duel.

Doesn't help that also people who play these OP classes like to troll, and play even more psychological games, like they say are not OP, while they are OP.

Which makes me wonder how is this level of harassment is even normal, like its suppose to be a balanced game for fun, but other than the imbalance you have trolls to add to the griefing.