As for the last boss, I found it extremely easy (even on Insane) if you bring along the Torque Bow and the Sniper Rifle. Use a Torque arrow to get the Kryll off of RAAM, then use the sniper rifle to bust his chops. When he gets close move to the opposite side (where he started), you can stick him with a grenade when you pass him by, but just be careful. DO NOT ATTEMPT TO EVEN USE THE TROIDKA TURRET since it's in the shadows. Make sure you stay in the light at all times, and keep an eye on your right and left flanks for Reavers just in case the choppers miss it. As with all levels, it's much easier if you have a buddy along with you (one has the sniper, the other uses the Torque Bow, then you guys alternate with the lancer and provide blind fire support).