the 20 potency is irrelevant, when you stack enough crit, I never use BB combo once I have aggro set, and never as an OT. Just SE and the odd SP for damage bursts. The thought of dropping SE or Maim bc of mechanics would be a bigger detriment to your overall dps than that extra 20 potency, again irrelevant when your SE hits are 2.9-3k crits.