Just increase their rate of fire to double to triple what it is now, make their damage drop off equivalent to Scattercannons, and make their cone of fire about 5 times what it currently is with massive bloom. Forcing one faction to have an extremely specialised unit whilst the other two factions have much more general units is simply wrong. The alternative is to give NC a decent long ranged weapon (don't say Mattocks, they're still shotguns) and give the other factions CQC weapons. TR and VS weaponry is simply too accurate and maintains a low time-to-kill over an excessively long range when compared to NC weaponry. Slugs are simply too inaccurate to be effective and can't be compared to the accuracy of VS or TR AI MAX weaponry.