Shaolong Gui. The Long Guis can be brought down and rendered immobile while you stagger and attack them. The Shaolong Gui doesn't fall so can unleash Bay and Quake at any point.
Recuperation - SYN/SYN/MED
Countermeasure - SAB/SAB/SEN
Combat Clinic - MED/MED/SEN
Tortoise - SEN/SEN/SEN
Buff up, Poison Vercingetorix, stay in Tortoise. When he uses Impenetrable Aura refresh your buffs, heal, then ready a full bar of Poison for when he returns to attacking. Rinse and repeat.