Weapons balance SMG vs DMR

I see that SMG are over-powered, even in distance for some of them. Compared to DMR like the M39 that is not played that much, hard to play and need 3 shots to kill at short range. You sometimes have hard time with DMR even at distance in front of a PW5A3 for exemple. 

I call for your opinion about a little nerf for some SMG and a buff for some DMR or maybe getting a new DMR with a 2 shots to kill capability at short range. I mean, it's already well balanced i think, but it can be better and more coherent do'nt you think ?