How are you clearing the green fire? If you're doing the tactic where you drop the purple next to it and wait for them to touch and explode there's something you need to know.
https://www.warcraftlogs.com/reports...s=1800&wipes=1
I'm assuming your shaman is droping grounding totem to help with soaking imp casts but this is dangerous because grounding totem actually can soak the void surge casts and if you're relying on the void fire to clear the fel fire and one gets soaked then the green fire will get out of control because you wont have enough purple fire to clear it.