The black Doubt bug

I'm currently Infernalist with the Black Doubt Hexer's robe equipped.
I think the demon form's health drain is bugged with the black doubt. Even if I stop the demon form, my mana still drained.
The mana drain stops when i unequip the black doubt.
Bug Report ID: #3958114993

Resurrecting this thread to say I've had the same issue, with full health my mana is still drained and it has something to do with demon form.