So far,I haven't had much trouble with the S/O. I'm using it right now, just to use it. I keep getting killed by gnashers all the time. 2 shots and I"m down, and they are still a good distance away. Really, I've found a counter for everything: S/O problem, use lancer or hammerbiurst, Retro chargers, use shotties, or just an AR till they are down.
I think it's balanced, though I would like to see a slight ammo bump for a hammerburst.
PS-16 kills away from gold retro in retail!!!
PPS- do king of the hill for the 100 kills, it's much easier.