Here is the deal. During the past few COD titles only a VERY FEW weapons have received a TRUE "nerf". What defines a nerf? Well, adjusting multipliers, adding recoil, changing fire rate is NOT a nerf, but an adjustment. A nerf is a decrease in STARTING STATS of a weapon. Say a gun killed in 3 shots at 50 feet, and 4 shots anything after that in it's bare bones form. If they adjusted it to where it killed in 4 shots at 50 feet, and 5 shots after that, THEN it would be considered a "nerf".
When they decrease a multiplier, LET ALONE ONLY ONE FOR HEADSHOTS, it is FAR from a "nerf", and if something that small makes such a big difference to someone, they should NOT be playing COD anyway. The amount of crying over "nerfs" has gotten to the point it's so ridiculous, it makes me want to pull my hair out. Look at BO2 when they added .05% more recoil WHILE HIPFIRING to the PDW. You would have thought that they made it a 20 shot kill weapon.
As it sits, most SMG's do more damage over range than they should for the sake of balance in a video game. Just as Snipers are FAR too accurate and mobile in close quarters than they should be. In all honesty, the damage drop off of a SMG should be close to that of a pistol as most of them fire pistol rounds, and have short barrels making long range accuracy pretty terrible.