At the end of the last level, if you are having problems with the final group of mercs protecting Doyle at the top of the stabilizer, the following is an easy way to deal with them. Slowly approach the ramp until you hear the radio chatter confirming they have spawned in above you. Then, back off and look up for the large fuel tanks. You cannot see them, but the mercs are gathered around and behind these tanks. Scatter throw all of your grenades at the tanks. You should have killed or wounded almost all of the mercs, leaving just one or two to deal with upstairs.