DRK has self heals in the form of using Dark Arts + Abyssal Drain (AoE damage heal + enmity) and Soul Eater (usually paired with Dark Arts to get a 400 potency attack with 100% damage healed). Which reminds me of another fun mitigation technique. If you're pulling a bunch of mobs, pop Blood Price and you'll have near infinite MP to abuse Dark Arts + Abyssal Drain for 15 seconds. When fighting one enemy, you should be using Dark Arts + Souleater as much as you comfortably can.