The shotgun in this game is actually the most powerful ♥♥♥♥♥♥♥ gun that's ever graced the planet, somehow outpacing the Doom Eternal BFG. The first few bosses are trivial as you can sit behind cover and plink at their weakspots with the shotgun, which has such a ridiculously tight spread it more or less guarantees every pellet will land on the target at any range, and the damage is so high per pellet it can kill the first boss in a few shots. It's definitely the powerhouse of the game by design which is why the ammo for it only comes in boxes of 2, but if you can save up the ammo through the levels (which is easy to do as even on normal difficulty, the rifle overpowers most enemies) you can atomize the bosses in seconds.

TLDR: VLADiK BRUTAL Shotgun > Doom 2 Super Shotgun