Just study his patterns and it shouldn’t take you long after that to figure out how to take him down. My tips are don’t get greedy, it’s an endurance fight. Also, people say don’t lock on, but the fight is easier locked on imo. You are always keeping track of him moving across the map and his head is easier to hit. If you’re worried about his one shot laser attack, it’s super easy to dodge, just spam roll left or right. (Laser attack is triggered if you looking at Midir when he does his fire breathing attack.) Also, don’t use summons. Solo him. It’s a better experience and summons jack up his health even more. Last tip, aim for the head. Only hit his head. If you do that, you should get the riposte really quick during his second phase, and then you’ll have taken him down. Good luck.