My suggestion is DOOM. Get to Dark Father with some folks and you can provo like crazy. Also you will have a chance for an arti.
Don't forget your Lolo's lute or a demon and undead slayer instrument for rotting corpses and Lich lords.

Oh yeah. Forgot to mention, if you are there with enough people, you can kinda hang back and pretty much train without getting hit.
If you fail on an rc or lich lord, which you will (I fail at 120 w/ slayer often) run around the circle of spawn until you can try again. I like to provo liches on each other or rc's on each other and then provo em off one at a time. This way if you fail, they will usually go back to fighting each other.
Legendary provo/ peace mages are the greatest chars in this game. If they would only let our skills affect other players we could take over the PvP world as well.