Overall I think both snipers and shotguns will always be a balance issue. if you can use them effectively, they will always beat out primary weapons, just because of their one hit kill nature. If you know your ammo spawns, you can run around the entire game with a shotgun/sniper/Fusion Rifle. I think special ammo availability is the real problem. Imagine if in Halo you spawned with a sniper rifle/shotgun and could use it for the entire game. You'd barely use a Battle Rifle since the sniper or shotgun has so much more kill potential. The way Destiny is built to have us spawning with these power weapons will make it very, very hard for Bungie to balance them.