Perfect Defense is valid, you also need to factor ENFIRE damage, and can also add double attack boost from Ifrit, add to that that you can give your party ice spikes, stoneskinga and hastega, SMN IS A MUST for the battle. You do realize that once SMN used PD, they are not useless, astral flow last 3 mnts, you can use convert or sublimation to gain mp back - and elemental siphon. So within the 45 seconds, summoner can add more damage via astral flow, add elixir and whatnot, they can actually do 2 astral flow back to back within 3 mnts, and still do another round of damage post astral flow with Heavenly Strike. Obviously you will need a very good summoner who actually understand the job, not some drive by summoner via abyssea school of leveling. SMN + SCH + 4 beast/4 monk is your ideal set up.