RE: The original question on the post...
DAVIK is INVINCIBLE! Don't waste any time shooting/grenading him - Calo Nord is your real target. Once you get him down to 1hp, the cutscene triggers. Davik dies by coincidence.
I have not verified this through looking at coding, but it has been my experience that focusing on Davik will get you killed, focusing on Calo breezes you through!