I always do good damage on Voidwatch NMs on BLM. We usually have 2-3 BLMs and assign them different spells, once we hit a HV trigger I'll chain-nuke Thundaja > Thunder V > Burst II > Firaja > Fire V and then go back to looking for triggers.

That's 20k damage in about 20 seconds, hardly irrelevant and there's nothing wrong with our alliances. There's nothing wrong with BLMs adding some extra damage.