The 2 molten giants before ignis put up a debuff called unquenchable flame before they die that is a dot that jumps from raid members and the only way to get rid of it usually is to either all wipe or keep it until u make it to the water in ignis' room. However, if after you kill those 2 mobs you have your raid all teleport to the expedition base camp, you can have everyone stand near the exit of the instance and 1 at a time run out if they get the debuff, since it cant jump between instances it completly clears it.