Shotguns have terrible range (prefer sniper rifle)...basically there isn't any application for a shotgun in pve. You may be thinking thrall killing is a good use. You'd be right but thrall aren't bullet sponges and they go down pretty fast and an auto rifle can make quick work of a pack of them, even a fusion rifle would do better. Bottom line, they're PVP weapons and nothing more and as far as nerfing or buffing them I'll still never use one in place of my sniper rifle.