Hrm. Tough one. I would have to say coming from wow taking things from it would not be a bad thing like:
an auction house for a better shot at a stable economy.
Outside of duels maybe organized pvp like battlegrounds.
And items, oh god items.
I'm one of those weirdos that doesn't pvp a lot. I mf fornhoirs clearing just about every boss/champ in hell for drops on my summon nec.
So a vast amount of items for all purposes would be good, and the potential for weird/unique non cookie builds like a
summon Druid, cry barb, bow sin, etc.
Just off the top of my head though.
