This is an endurance (you can read that as tedious) fight. You don't get soul on hit so spell builds won't work and they elected to go the "quadruple his health" route for difficulty.
Unbreakable Heart
Unbreakable Strength
Mark of Pride
Grubsong
Sprintmaster
Essentially outlast him. Assuming you're getting hit, grubsong allows you to heal when he's stunned. You fight him for three rounds. You've won when he gets stunned the fourth time.
Play "very" aggressively. Kiting doesn't work, you want to be up in his business any time he's not hammering. You're going to want the cloak from the abyss for dodging through his ranged attacks.
Ignore any recommendations for the spawned spiders or the charm that damages what you're dashing through, they neither give enough soul or do enough damage to be worth it.