Sounds like you might have had Gale knocked down by something (maybe he was low health after the fight and pathed into a trap?). If Gale is knocked down and dies his body gives of a necrotic miasma that damages those around. You should get a cut scene for this partially explaining why the first time he is killed.
True, which is also a problem. I noticed the damage keeps ticking on the background while you are locked in a conversation with the....what is it? A sentient vision? I dont know but it caused me multiple character deaths already xD
