Last time a 3 skull boss has been a challenge I was new to this game, with an Iron Greatsword and was facing Sand Reaper Queen. It was cool to dodge her attacks and hit back.

Problem with thralls ? They have too much HP.
You want to give them less HP, they become totally useless cause their AI sucks.

So it’s just a dumb tank challenge: you have good thrall and proper equip ? You win. Otherwise you lose.