i beat mission 63 in ch11 (after killing the ch 11 boss which gives u to CL 9), so it is possible
start off with fang enchanter with buffs on 3 characters, summon, then buff bahamut (with haste and bravery), switch to jammer, after that few debuffs switch to attacker and dont go into drive mode. once all ur characters are out switch blaster/blaster/blaster until 850-900%, then attacker/attacker/attacker, and use highwind on fang when the tortise about to get up
Though at the moment my Crystarium is only level 8 (i only just started Chapter 11 a short while ago) and i haven't even maxed out any of the Roles that were unlocked at Crystarium level 8 yet. So it'll still be a little while yet before i can pull that off.
If you want to beat them then you need upgraded accessories so you can withstand that 9000+ dmg stomp. --- Good Games: 360/12 PS3/4 Wii/2 PS2/Lots XBL:Felix N Phoenix PSN:FelixFelice Wii:Felix/3652-0173-5553