my opinion from experience in KO i think Bp it's the king of PVP as long there r not more than 4 lvl's between bp and the other character.
Just think of that : parasite,torment,and cut a bit of app so r u still able to fight against him?against hellis skill? i guess not.
he can have so many jobs,healer,buffer,debuffer.second one is rogue.
rogue can also be the best in PVP but it's let's say almoust impossible to win vs a good bp.rogue is a character who have minor(the best source of healing).i think mages are the 3rd and obvioustly can be 1st but only with babashop items and lvl 80(they can jump at that lvl).warriors r useless if r solo because let's see the reality.no heal,no duff,only defence,hp and app(bp can use duffs),but they r the best with a healer behind.
this is only my opinion and i say that from experience.i play KO from the first month of launching,changed 3 servers and i'm still in shape
cheers!