The damage threshold damage was increased to 15%.
Shotguns are currently more useful against unarmored animals compared to (armored) NPCs. On the one hand it's a nice idea that one weapon type is more effective against this, and one weapon type is more effective against that, but I agree that shotguns should still be able to do some decent damage to NPCs. Especially since it's not very difficult right now to find armor with a higher DT than the damage of the average normal shotgun projectile.
But increasing the damage would probably make it overpowered against non armored opponents. You could also increase the damage and reduce the number of projectiles, making it more effective against armored opponents but not overpowered against unarmored opponents, but then it's not a real shotgun anymore.
Damn, I can see why the Damage Threshold system is such a pain to balance right.