He walk in middle of enemies and undergoes a deluge of bullets (I also think, one militech's guy have HMG). He is in "I feel nothing" modehmmm, I'm not sure. is that area harder than the secret area ending? I beat that with an h2h playstyle. Or is it more the way he does it that you are talking about?
In very hard, i don't know how it could be possible to survive more than 5s (even with 7K armor).
I also do easily "Don't Fear the Reaper" (with 3K armor), but by avoiding at maximum the bullets and healing me when i'm too low life