First Phase: Oil & Okinaga’s Flame Vent + Living Force melted him. Dodge his grabs (jumping away or to the side worked for me) and you’ll be fine.
Intermission: Healing Gourd, Mottled, Divine Confetti and make sure you have the Umbrella equipped.
Second Phase: Block/Defelect what you can or run. Attack during the openings. Use the umbrella to block the terror attack and strike.
He’ll be down before you know it.