I think the main problem here is the way bink works (or rather, doesn't work) - no matter how much you're binked, you still have 33% chance of hitting exactly where you're aiming. Until that's fixed there's no point in trying to fix barrett's balance at all, as it will still be a flawed weapon.
Other than that I personally don't find many issues with it. It's a long-ranged weapon that has many cons in close range (long ass reload, bink [kind of], movement accuracy). When you do miss with it in close range - you're pretty much screwed. If bink worked properly - I think it would be a fairly balanced gun. My only issue with barrett is that there's no way of spotting a sniper off-screen, while he gets a head start thanks to the zoom. If you're up against a skilled sniper - you're in for a very frustrating duel where you repeatedly get killed without even seeing it coming.