The problem with Scout rifles is not that they are too weak.
Some can three shot people. And otherwise acurate people can make effective use of Scout Rifles anyway in PvP
The issue with them is that PvP doesn't have a lot of maps that allows them to show their strength strength, Sniper rivalling range.
Which is a good thing.
Snipers aren't too inherintly strong in PvP save for some "lanes" that give them a long line of sight.
Invective.. while a pretty good shotgun all things considered, it's ammo regen is a tad slow anyway. Maybe the oncoming ammo adjustment for special weapons will be align with 30 second spawn timers, Invective's regen would only save you having to go to the ammo chest.