So long as enmity does not reset, yes. To use your Tsukiyomi example, you can dump aggro after add phase since it doesn't reset. Construct 7, on the other hand, does after his mid-fight transition. So it'd be a waste. That said, be mindful of whether you can get another use of something like Lucid. Using it going into the add phase is better as it will be off CD, thus allowing you two casts instead of one.