After watching a couple of videos like this one from youtube :
I checked out myself , and what do you know ?! top players (not all ) but almost all , are boosters , so I started to report them for boosting after watching their channel . So please Treyarch do something about them . Boosters all around gamemodes , maps , etc... clean them up
Yes, there are boosters and you are enabled to report them- in game. You should identify them and report them, not a problem. Just do it during the game or right after. As long as they are in your lobby, you can report them. I frequently run with Engineer which gives me fairly good evidence as to their boosting places of interest.