The attackers always lose because the level is very unbalanced, and it is a giant funnel. Unless you get stacked teams or a bunch of people working together the attackers have no chance. Personally I am only taking away gameplay mechanics from my time on Metro, because Caspian is so, so different.
Metro blows right now because everyone just goes prone.
Seriously prone is the dumbest thing ever.
Also. Headshots only seem to matter to bolt action sniper rifles I guess. I'm constantly headshotting people with other guns and they take 5-7 shots to die.