Thugs/Dark or Demon/Dark are probably the most powerful MM combo's. The amount of debuff offered by dark is ridiculous, when you hit 38 it jumps to solo'ing just about anything levels with SO's. In pvp 1v1 it was pretty much unbeatable. I had built a bots/storm MM that I spent roughly 150mil inf on, I was beating 3+Bill inf builds 1v1 and pretty comfortably. The thugs/dark could have easily done the same with even more ease. The double stacked AoE heals/tar patch/intangible was just insane. If anyone did come close you just black hole them reset pets and you're good to go.
So yeah when the game launches and you wanna have a god like feel, roll this. If you want to farm, build elec/fire brute. Between these two builds you can conquer pretty much any obstacle.