I feel that this could be countered by not playing bad.
As True as that is... when your just coming back to the game after a long break (Which i think its a safe bet that millions are) and your only option is to pug the CM's, you can't make other people not play bad.
Taking a warlock through the whole dungeon just to make the last boss slightly easier is pointless. You will have an easier time to just go with an optimal comp.