RP 4 Claimh Solas

Melee works perfectly fine. Don't attack him from the edge of his hitbox, instead get up close and personal, standing slightly behind him but still on top of his model. Since you're behind him, his life drain and dash attack will not hit you. Unlike most monsters, he actually has an animation for turning around which wastes his time and let's you whack him more during it. Any time he turns to face you, move straight through him to get behind him again. If he does his AoE attack, ignore it and keep attacking. You should have enough potions to kill him before you run out from getting hit by the AoE.