Currently 5.56 NATO and .308 do very little damage compared to what they do in real life. Even the man without armor can stand two or three hits with 5.56 at 200m or less. It is not quite an issue in CQB (if you use burst fire) but when you engage at medium and long ranges it makes some trouble.
The problem of low damage affects .50BMG as well because civilian pickup truck's engine requires at least 2 hits at point blank range to be disabled.
You may say that in real life man will survive after several hits -- yes he will, but he will be combat ineffective for at least few hours (or even days and months) which means he is out of combat anyway.
The easiest and the most effective way to solve the problems is to increase weapons damage.