Gluttony of Elements Doesn't Heal

Gluttony of elements from Blood of Corruption is not healing.

Test setup:
Blood of corruption, righteous fire, -70 fire res, soul rippers for soul generation, life flask to recover life.

1. Generate souls using soul rippers in hideout
2. Drain life to 1 using righteous fire
3. Use life flask to recover some life, roughly half
4. Use gluttony of elements and quickly activate righteous fire

I would expect for the righteous fire fire dot to heal while gluttony of elements is active, but instead it seems to be neither healing nor damaging.