Honestly beating this would have been near impossible without Regening health. The reason is that the Mosin Nagant kills you in two shots, and it becomes more common the farther you get in the game. Plus most roof snipers spawn once you get "in range" and they already are in alert mode looking for you. Even if you hide behind cover and edge yourself out, there is a good chance they get the first shot off first because AI lol. Shit, I once edged out of cover so I could just see a sniper's arm. I got shot, which threw off my aim and the shot again before I was even finished flinching in pain, killing me.
Is it possible not getting hit? Yeah but it is really difficult and requires memorizing where everything spawns, which takes away some of the satisfaction IMO.