I think the Living bomb is overwritable in PVP vs players, just not on mobs. Not sure why either. I like it the way it is with mobs for sure.

sidenote, for some reason my mage had better dps with frost than with fire, probably had to do with the /castseuence function sucking but could have to do with the super spell buffed features of a shaman druid paly mage type team.