Actually, the sniper is op. Perfect aim, even when no-scoping. inst kill and perfect for all ranges.
so you kinda need to add more weapons if you want to keep the sniper as op as it is.
The other guns are perfectly as good. The sniper has little ammo and a long time between shots, which is plenty of time to kill them with the rifle or shotgun. Being good at using a sniper means you have to have excellent aim and reaction time, or you'll miss your first shot and die. It's balanced as it is.