Couldn’t find a bug reporting section, so I’m putting this here, because Galilea is the only one who I’ve had this problem with.
As the title says, when you purchase Burning Sunset, a legendary pauldron that blocks an enemy ability every 30 seconds, it will also block the healing component of Abyssal Form. If you gain cooldown reduction casting AF twice within 30 seconds WILL heal you, so I’m almost positive it’s the item blocking it.
It may also block Miko’s mushroom heal, however I’ve gotten conflicting results from trying to test this.