And as ShunNakamura said, be sure to have someone with the Thief ability "Steal Weapon" in your party. Get that Blood Sword and disable Gafgarion A.S.A.P. If you don't have a Ninja yet, bring a Thief with 'Item' as a secondary ability ("Throw Item" too, maybe). Use him to steal the weapons from the enemies and heal himself and others with Hi Potions, X Potions or whatever.
And it's always a good idea to go back and level up a bit. Figure out which skills you'll need for the battle and be sure you've bought them.