Do it slowly. Fighting guns blazing will get you killed in seconds. Once More was a must have for me in this battle. I'm sure you can go without, but with his long combos you have to be very careful about it. I struggled with him too, but I don't really have a specific strategy with him. Just keep your distance, stock plent of cures, if he isn't rushing everywhere throw in a shotlock, the normal stuff.
I got him in a corner (somehow) and just kept hitting him. Shotlocks were great for this, I dont remember which one I had equipped. Once more and Leaf bracer were great. Leaf bracer allows you to heal without getting interrupted.
