While I don't think that it is really OP, it is definitely a far superior weapon than the M4 for only 50$ more. I personally think that they should just increase the price back to where it was before. Teams already know how good it is and will probably still buy the gun for certain situations.
If Valve decided to keep the price the same, I think they should nerf it by completing changing the spray pattern of the gun. This is why I don't mind the SG 553, it still take some time and skill learning the recoil pattern of the gun. With the AUG, its pretty much the same pattern with the M4, and you have the scope to help you out.