i found the last boss(es) too easy, as i had thousands of minerals left after massing the rocket launchers, and after i didn't really have room for enough, i upgraded them. then built a few pulse lasers to protect from missiles, and it became ridiciously easy.
no.. flame thrower. then buy all the perks to it. then buy all the perks for hotgun. then buy the special perk for shotgun. after THAT it's super easy.
SORRY FOR DOUBLE POST!!!kind of a cheat:if you want high lvl refined weapon, save before refining. if you fail the refine, load the game and try again. every time you succeed save. eventually you will reach lvl 10.
the last far east katana skill kills the leaders with one strike... then you just equip/sell their stuff. game becomes too easy if you do this, so not recommended...