From what I can tell, the difference is mostly that instead of rolling with boring people like wonder woman and superman, you get to roll with completely deranged and hilarious lunatics like the joker.
Also I doubt you get to joker-bomb people as a Hero.
As for max levels camping low level areas... Yeah, you'll get that a lot in any new mmo on a pvp server.
I've gotten quite good at escaping their half-assed attempts to take me down. Then again, I am level 22, so I can survive a hit or two from them before going down.