First you seem to believe the MTAR is still the only viable SMG choice and state that as fact when it is in fact just your opinion. The reality is the added range and (in varying combination of) better recoil, better ROF and/or better hip fire of the other SMG makes them very competitive with the MTAR and, depending on the map, potentially a better choice. It's not all just about range otherwise the sniper rifles would dominate on every map, which they don't.
Just today I played a game on Stonehaven and had several players using veprs or vectors (can't remember which) and they did very well on the longest range map. This was a map a few days ago I was dominating with an M28 and muzzle brake. Now my opponents did try to shorten the range on our engagements but I can say without a doubt they were very competitive and ended with the highest scores on their team.