Blood Mist: "Entering this form removes and grants immunity to all disabling and immobilization effects, but you cannot be healed by any other ability and your Magicka Recovery is disabled."
Critical Surge procs still heal you during blood mist.
DSA Regeneration Staff grants you magicka every time it crits during blood mist.
Spell Parasite grants magicka during blood mist.
I don't think the ability is overpowered with these interactions, and I really appreciate the quality of life fixes on mist form, like it being a toggle ability and especially HoT abilities not being removed just because you enter mist form.