I will shield swipe as long as I have adequate enmity lead, and I rarely don't.

Shield Swipe is best spread among all the mobs in a pack because it helps reduce damage done to you (no-ws has diminishing returns). In a long fight (such as chain-pulling in Stone Vigil) you are bound to slowly deplete your TP, and Shield Swipe becomes a very nice balance between enmity and resource. After all, you only need to do enough enmity. (I try to keep all damage dealers at least below 70% though. You never know the good ones are holding back their potential, because they're the good ones.)