I have beaten it with different party combinations pretty easily. My favourite tactic is equipping everyone with shadow absorbing equipment. Vivi casting Doomsday, Dagger summoning Ark, Zidane stealing and Freya using Dragon's Crest. No heals are needed because Doomsday heals everyone. Sometimes I have to throw a few Remedies, but that's it.
For me, the strategy for beating the boss is going all out, not wasting time on healing. I maybe a bit wrong, it's been a while since I last played this game.