If you keep running into situations in which you get "oneshot with no counterplay" then the problem doesn't lie with the game but your awful playstyle, I'm sorry.

I use HC + Sniper and I'm fine with people running at me with a shotgun, using pulses or telestos. Simply play to the strength of your loadout rather than calling any other loadout overpowered. Don't be an idiot. Shotguns and Telesto are only effective in their specific situations.

You can shoot telesto projectiles did you know that. Also CoD has some of the slowest TTK out there with basically no headshot multiplier existing in the current game. Shotguns don't actually oneshot in that game. And I know that without even playing that game.

Maybe don't get angry over things you don't understand?