The title says it all. The carb-9 is easily the best automatic close to mid-range weapon. I remember hearing that Splash Damage was balancing each weapon thoroughly and yet they allow an SMG to be a better option than mos AR's at any range. In my opinion they need to increase the recoil and reduce the range of the SMG's and this will convince people to use another weapon besides the carb-9. In competitive matches on Gamebattles for instance all I see are people running around with the carb-9. It's severly limiting the weapon diversity within the game.
The SMGs are better at most ranges than the ARs if you insist on holding down the trigger till things die.
Try limiting your fire to bursts with an AR and you will find them to be some of the most efficient weapons in the game. The Gerund can pretty much snipe people if you keep to 1-3 shot bursts. The Euston puts out a TON of damage. ARs also dont have damage fall-off while SMGs do.
But yes, the SMGs are effective weapons, and that's because they are a main weapon for light characters. Have you attempted to play light in multiplayer? its pretty difficult to take people out when you are only given an SMG and a pistol. Can't imagine how it would be if they nerfed SMGs.