Adrian has a large health pool, but fairly predictable patterns.
He initially spawns one totem that drains you of health, while healing him. Take these out when he spawns them ASAP. He will also summon skeletons and skeleton mages, use them to fill your Overdrive.
When he drops below half, he will start spawning 3 totems, again, deal with these while dodging his attacks. And killing skeletons.
You can stun Adrian with the "Point Blank" skill (
), so use that when you see an opening to get a few more licks in, or to interrupt his summon.