hope this helps, and hope it aint to much detail.
get the machine gun (the para like one) and sniper rifle from the armoury before you go out.
Use the sniper rifle to take out the machine gun guys (easiest to get them before they start moving)
Use the machine gun on the big guys, aim for their head.
I didnt move far from the door until they were all dead. Thats about the best cover you get and if you keep the big guys below you, rockets hit the edge of the ledge.