i was all members lvl 99 and still had trouble.

ninja- masamune & the boomarang thing
devout
knight- ragnarok & excaliber
final blk mage (cant remember name)

i used curaja every turn with devout, attacked with knight, threw what items i had with the ninja and atked, and the blk mage i cast top lvl spells and used as back up with items.

my tactics are very simple, Kill the Beach quick and dont hold nothing back