Haven’t touched campaign yet but enjoying multiplayer and zombies, Prestige 1 level 27 atm and I’ve already seen people who are like midway through second and even a guy earlier who was one level off of 3rd. Guns definitely need tuning because the mp5 is just broken in some scenarios and snipers...
Its retros, there's always gonna be people like this, in a way its good because it helps you find out the vulnerabilities and potentially block them so it doesn't happen to you again but there will always be people who do this stuff purely for their own entertainment