Mythbusters have proved a man could take 10 rounds to the body of 223/5.56 AR 15 rounds to the body and not immediately die and keep returning fire. It's a fact however a shotgun to the chest is 1000× more likely to lay you down for good in 1 hit. It's designed for knockdown power. It is still realistic no matter how you complain about it. And I don't even care you use shotguns and I defend it.
In Battlefield 4 Assalt class could equipt 3 Shotguns at once. All which were a one shot kill close range and it never destroyed the game. It is "realistic". In real life a shotgun would dominate a close quarters engagement. In my opinion the shotgun does exactly what it should. With that being said... that does not force you to use it... it forces you to use logic and other tactics other than just blindly running around corners into a guy with a shotgun. For example, before entering an area... aren't flash bangs in the game? It still comes down to a person's skill with using the shotgun. It's not a sniper, and if they miss the first shot, they likely won't survive. The games becomes totally fake if a shotgun does not kill you in 1 shot close range.