If you don’t mind cheesing this boss, you can use a pet build and stay on top the arena, only coming down to heal or hit the boss when he’s staggered.

He tends to jump attack 3-4 times in a row if you stay close to him before he switch to the slam/shockwave attack. You can dash behind him when he jumps and punish him between his jumps and then distance yourself after the 3rd jump or so to bait his shockwave and then repeat. It's not perfect but with a fully upgraded nail, quick slash, and steady body you should be able to stagger him pretty quickly. Shade cloak helps.