First of all, don't fight him down on the ground. There's a ledge near him that you can stand on when you're fighting him so that you're level with his head; as long as you're up there, he can't use his Titan Stomp on you, which is his strongest attack.

Also, hopefully you've done the quest line that results in getting Monado Armor for Shulk by now. Level it up as far as you can; it will make a huge difference in reducing how much healing you need. I think that I used Shulk, Dunban, and Sharla against him, although you could probably swap Sharla out for Riki or 7 out for Dunban.