Not really if you look at weapon attack, attack only applies in pve. That's what makes the weapon stronger against enemies. Impact is your weapon's true damage. The attack is a multiplier of sorts, not sure how this is calculated, and that's why you end up doing 3-4000 damage against pve enemies. But there are other factors too. Like level resistance and enemy type. They probably just simply made the enemies take more damage from shotguns. They didn't raise the damage on the shotguns themselves.