lol:P my team is around the lvl 55 and i beat it with a tactic.
the best way beating it is to set this team up:

BASCH,Penelo,Vaan,llyud(always good for revive)and kytes.

tactic:beat the monsters on the side and capture the middle summoning gate. set gambits:
kytes flare and penelo holy.
if you got bahamut you summon him and wait for mega flare is ready! let llyud do revive if
someone gets killed by final eclipse. make sure zodiark can kill only with final eclipse
and not with graviga. let basch and vaan attack with melee kytes do flare and try to keep
it up.
quickening hint is to summon on vaan and kytes.


USE THE QUICKENING NOT ON ZODIARK BUT ON THE DIABLOS AND MINATOUR

and the most perfect hint is to summon much carinbucle as you can. if not??? llyud will
get killed and penelo too!
you will not can revive.


Last hope is too run away and revive the fallen and summon

GREETZ

Capture middle portal team don't matter u just need espers and bahamut helps let everyone
fight and die but vaan then summon espers and let them atk and die keep running away with
vaan when espers die vaan gets his special and when he does use the special on zodiark and
repeat until u win