About balance... somehow, yeah, I miss Aion Templar gameplay or BDO Lahn.
About PK and "Open World"... It's not as easy as to just "open a server". The game is not designed at all for that purpose. And among the player I know, none is starving for PVP (me neither, only RVR format from time to time, that's all).
I don't believe in "Open World" for a simple reason : even the Abyss in Aion tended to be desert unless it be during Fortress conquest. People were coming for Dredgion and Fortress and were doing Orda-suicide when it is supposed to allow a PVP encounter 1v1.