Shotguns in pve has been neglected for so long and all that it is good for now is just for one two punch builds. It did look like you tried to make them more viable when you added Chain reaction to them, but it wasn't enough. Even worse is that you nerfed Chain reaction just because you wanted to add it to more weapons. Similar is the destabilizing rounds that causes void explosions. This one is much better than chain. A simple damage buff is all that Shotguns need.