Killzone 2 gave their sniper class an Invisibility Perk Which was nicely Balanced When prone, and still, the snipers body was invisible(But their suits red/blue eye slits would still remain visible and glowing) And if you looked in a hiding snipers general Direction their name would pop up in Red. The sniper was mostly invisible, But the Invincibility gave a bluish tint to the snipers vision, which made it a bit more difficult to aim with the ability on.
Combine that with the fact that KZ2 combined the sniping ability with the SIXX-AXIS control.(Your sniper rifle's accuracy was effected by how well you held your controller in real life. Meaning if you shook your controller, the rifle would shake, If you tilted your controller up, Your rifle would tilt up, etc etc) And the sniper class was both fun, and balanced, at the same time.
Sadly tho they listened to the COD whineboys, Took out half the things that made the sniper class balanced in KZ3(like the SXXAXIS) and worse of all, Gave the sniper class the Helghan assault rifle.
So at the begining of the MP, You'd have snipers camping corners with assault rifles and invisibility turned on. Was a nightmare. GG patched it to be a little better by giving the invisible perk a shorter lasting time and a longer recharge time. But the best way to balance it would be to take the AR away from that class.