Shotguns have a very specific purpose. In order to do well with a shotgun, you have to dictate every gunfight. If you're consistently losing to someone with a shotgun, it's because they're dictating the gunfight.
I gotta say, I always hated shotguns in the other cod's (striker is still my mortal enemy). This game though, I had a rough string of matches where nothing was going right for me, so I said screw it and created a shotgun class. I figured if I'm not going to do very well might as well use a weapon I'm not good at. I actually had my first solid match, broke even but I was happy. The next couple matches I played with it I did moderately well and have started doing better. It was my slump buster lol. And now, I have a gold shotty!