When you first get off of that elevator kill the steatlh dudes behind the boxes on the left. There are 2.

Next I stayed near the elevator and sniped all the enemies sitting right on top of the doc.

Then I stayed back and killed the ceiling guns with chain laser and engaged the round 2 guys that are off to the right of where the doc stands.

This was the most frustrating point of this level. I think I had 5 or 6 restarts. By the time I got to this point the doc was almost full health and could take a lot of punishment before dying. I almost always died first.