I'd call a 450 priced gun that can take out tanks from long (invisibly limited) distance as OP
Regarding Voltie, Jake's got a point. My Mendoza blocks GDI invasion on X-Mountain for about 10 minutes without dying. It pierces through tanks like butter.
But once enemies starts rushing infantries that is agile enough, using Volt rifle to stop such rushes would be an achievement of itself. Small hitbox, ridiculous recoil, dead fast ammo depletion... it is not a good combination. The range is not at all visible, as I could hit far just quite fine. However, when you start using volt rifles on a bunch of infantries... you're just Renegading it wrong