Yeah, you can deactivate it but that 10% is not a big difference anyway. Conflags will still kill you if they don't destroy them, Divebombs will still nuke your party, the walls will still kill you, the snakes will still wipe your tanks, the twisters will still one-shoot you, the Dreadknights will still vaporize your existance, the Liquid Hell will still be a pain. We won T5 last night without the buff, because we think the same than you, but then, we didn't notice a big difference between having the buff or not.