Well, yes Du'un the Thousand Sons are a pretty good choice, they have some of the strongest psychers and are generally considered superior to other traitor legions.
Well I know you don't want to hear this but it is all a matter of perspective and situational context. All of the Traitor Legionaires (other than maybe the Alpha Legion-although they are the only ones that are actually recruiting and keeping their numbers) are strong in certain ways.
