Combustion is a useful armor, the regular version is a little stronger than epic boos plus armors. Is useful cause there are lots of water and magic armors in arena, but is countered by the army of earth armors. You should be aware of clayplate mantles and similar armors, but is an useful armor anyway. About the low star fusions.. I fused two sky guardian while making wind monarch and exprcist vestments. Cloudrange? Not fuseable for now.