Can't beat the XII ultimate+
Team has gone through several evolutions in the attempt, first Raines was switched out because holy/dark were a hindrance for this fight, switched Yshtola back in, then Rafa was switched out because of general squishiness even though her Burst was still kind of neat, sorted Shantotto out and slotted her in.
Terra L80, Dispel/Curaga, OSB/Burst/Super, Mako Might
Vanille L99, Esuna/Shellga, USSB/Burst/Super, Dr Mog's Teachings, has Major Silence resist accessory
Yshtola L99, Protectga/Wrath Burst/Wall/Aetherial Pulse/Medica II, Ace Striker
Shantotto L80, Blizzaga, Thundaga, Chain/Burst, Attunement II
Onion Knight L99, Power Break/Magic Break, OSB/Burst/Blowback, Battleforged
Roaming Warrior - Wall
General gist is to try to get Vanille's Astra off right away to protect the team from status, somebody summons RW to Wall, Ysh and Vanille on Shellga and Protectga duties, Ysh then wraths so she can do her thing, Onion uses breaks, time is spent building soul gauge, healing, etc, Onion uses his Burst once available, then Terra lets off a Super, while Shantotto is on Blizzaga and Thundaga duties, Onion is on swift spell duties, Terra is to do an OSB after Shantotto's Thundaga, she also has to Dispel once the boss enters Enrage/Short Fuse stage. Things usually go pear shaped before I can really get Shantotto's Burst going for the end of the fight~
I haven't really tried much since getting Shantotto to L80 since I drained my battery trying to beat the fight ;P So hopefully I'll be able to beat it eventually.