Just did Ultimate twice. This fight is definitely a step up in difficulty from Garuda.
Typhon has 3 moves to watch out for:
Special (used randomly): Clears all debuffs
Overdrive (normal): Does 1-1.5k damage to entire group, attack up on Typhon
Overdrive (rage): Does 3-3.5k damage to entire group
Cassiopeia is your best friend on this fight to clear the ATK UP buff, and also for the extra healing. Debuffs are less effective since Typhon regularly clears them. If you have DEF DWN, you might want to save it for your Burst. Otherwise, buffs and raw attack power will serve you well. The goal is to clear the boss before damage accumulates; avoid letting the boss get off an overdrive during rage at all costs. Clear ATK UP buffs immediately (including on trash), or the extra damage will overwhelm you. DEF UP buffs are helpful to mitigate the AoE damage from the normal Overdrive.