A Change to engulfing (maybe also Nox Breath) would help. let the %firedmg amplifier scale off magicka and SD, so a Tank cannot provide the full power of this debuff.
Despite the tried and true debate method of lol at someone's argument, yes, it's a burst heal for a tank. It's just not the burst heal you want for a dps. And I'd argue that a burst heal can occur o
Dark Cloak could do with a magicka/spell damage scaling on top of the health scaling like Coagulating Blood so magblades can have an additional HoT without needing 40k hp for it to be worth running.