If its a fight where you need to stay in Defiance a lot, its one more offensive CD. If not, you can use it on pull for burst enmity and then again when its off cooldown, and you're in Deliverance, swap over into Defiance with Unchained and its like a pseudo-defensive CD as you gain the benefits of Defiance with very little DPS loss (assuming you're tanking most of the fight in Deliverance).

I'm curious who/what/when/where/why you thought this skill was needless or unhelpful? o.o Its a pretty self-evidently good CD.