Seems you've already beaten them by the time I noticed the post...sorry I didn't see it in time to be of help, answering the question, I just haven't been online as much since Christmas Day, got a whole bunch of new video games to play, and they are definitely nice.
Well I am glad to see you have clearly been victorious over them.

Did you get someone to help you defeat them? Only reason I ask is because I imagine you may run out of MP against so many enemies with the amount of HP they have, if there is nobody else chipping down their HP with weapons, as well.