Dohati can be an annoying battle for those who are not prepared or get careless with attacking. He only has two attacks - a physical combo that hits from 400-900 damage on a single character and a multi-target attack called Chaos Breath which hits Spirited characters for 300+ damage and un-Spirited characters for 900-1100 damage and has a chance of inflicting Venom and/or Toxic to all party members.
Dohati's attacks are all Dark element, so equipping Ebony Jewels on party members is a good idea. Aside from that, Pure Amulets and DEF boosting accessories are good choices, and perhaps an HP increasing accessory for Noa, so she can survive a full power Chaos Breath just in case. Additionally, giving Noa a War Soul can make her Miracle Arts more potent. Vahn and Noa should have absorbed Orb before the battle, and one should at least be Lv3 so it can cure the status effects if no accessories are available for that purpose. Gala should actually be an attacker in this battle.
At the start of battle, every party member should use Spirit, as Dohati will always start it off with his Chaos Breath attack. Taking the full force of this attack will usually kill Noa and take Vahn and Gala to critical health otherwise. Dohati gets noticably smaller after using Chaos Breath, and his size is a hint as to when he will use the attack again. When Dohati gets hit by physical attacks he will grow in size, and he will still grow slightly after each round. It usually takes about 4 turns for Dohati to use his Chaos Breath again, and it is a good idea to Spirit with at least two party members at the beginning of every fourth round just in case.