Judging from OP story, I find it quite suspicious. Most likely that MNK & healer are actually spiritbonding, judging from their unusual low HP. Not that I against SBing in dungeons since I did that too, but when they realized party performance were getting bad, the SB players should consider switching back to their best gear. Or can just leave.

OP's not doing anything wrong. It's the tank that didn't realize party's overall capabilities and just ignorantly trying to rush things ahead by requesting those unnecessary AOE. If the tank actually planned to speed run, he shud do quick check if his party are quite up to the task.

IIn OP's place, I would do alot of those sleep spell on mobs instead, if they not resistant to it.