Yeah it’s insanely hard. Played through the game a dozen times and it’s one of the few bosses I still walk into the arena and think “welp, time to die.” So you are 100% not alone, summons make him even more unpredictable and he can just turn around and delete you.
Thank you for posting! It was a lot of fun to see these posts in my feed and they always brightened my day. LLAP as well!