Well aiming down a sight would make it more accurate than firing from the hip... no where near as much as lying still in a prone position would but it'd be a fair improvement over firing from the hip.
Quick scoping isn't aiming down the sight though, it's waving it in front of your face. That would cause so much gun wobble that the only person safe from a bullet would be the person you were aiming for.
And if you resent being killed by "Shotgun in corridor" people, Brink probably isn't the game for you. It's confirmed that the game will be more focused around close quarters rather than long range snipers. As everyone has been saying. This isn't meaning to be offensive, it's just true.