While not in the upper levels of the Dominator tree (mines Grav/En, since hes wearing a tech suit I figured it fit.)
I actually found malicious harder than vicious, Ruthless harder than Relent etc etc. Due to the number of enemies.
1 target.. I could take (unless it was an elite boss or AV) but if there was more than 2 I was always in trouble. So in a group I'd often pick a lt to keep held the entire battle, and throw a boss all around the place so he couldn't hurt anybody. (lift, power push and propel rotation)
Dominators I actually found rather powerful but overwhelmed easily. I also found the playstyle matches the whole sadist description in the manual, as you very slowly, incapacitate and destroy 1 target. (Does make solo'ing take a long time tho lol)
Only lvl 20 atm, so this is just what I've seen so far. Liking the increase in Domination too.