You are talking about your mission "The fallen" right?
Imho you should use either JAM hd ammo or some of the bullet dispersion scripts submitted in scripts/beta testing because i for one are sick and tired of getting sniped by mg-gunners and other loons that i can't even see, plus this would make firefights last longer.
I think this is a problem with most missions i've played but i'm not a skilled player, i've spent more time in the mission editor and playing around with addons.
Maybe other players thinks the "ai sniping" adds to excitement?
Anyways just my 2 cent, happy mission editing.