I made it through what appears to be most of the story. I made it to the point after you set the c4 and talk to the secretary. The section after that, I find annoying as hell. The first time through, the guy with the shotgun 1-shot me.
When it reloaded, my assault rifle was gone. It didn't load. That left me with my silenced pistol. It makes it hard to run-and-gun through that section, which you have to do, when you can't hit anything and you die quickly when you miss.