This is is probably the highest DPS spec for Arc/Fire. With the change in Living bomb it is well worth just putting it up on the boss as a dot while you keep firing away. Between points 41-45 there really isnt much to spend on so i went for World in flames and flame throwing to help out on range and Living bomb (I couldn't really find anything else that would help DPS) While i see this as an issue i still think without LB and Burnout your really gimping your damage potential in the fire tree. If you were looking at making a more Arc/Fire hybrid relying less on fire I see this as more optimal then your build.