killing raam on insane on your own takes a loooong time. i flew through insane, theres a few tricky bits (like on top of the train with the troik guns)
but killing raam is enough to drive you mad, at this point i didnt know what co op was all about i wouldnt have thought you got the achievements so i just plodded on my own. basically it takes twelve active reload torque bow hits, 3 good hit grenades and about 500 round off the lancer. biggest problem is avoiding the fucker long enough to get that lot on target. good luck anyone who beats it, because i know how hard it is i almost gave up. you gotta keep dom alive and hope that he acts as a decoy while you shoot. easier said than done though