Genereally the best way to play mutilate build is to stunlock your opponent, so you can always stay behind them, when you're solo anyway. Usually it goes CS, mutilate, KS, mutilate, mutilate, eviscerate, dead mob.
When you're talking about grouping though it's very different. You can still do the stunlock approach for the additional combo points for quicker eviscerates, but bosses and such can't be stunned anyway, so you'd want to be using ambush or garrote there.
Really it's up to your discretion.