All you have to do is look to a sport like baseball and see what types of players are doping. The best of the best doped. Sosa, McGwire, Bonds. And then you had a bunch of average guys get caught. After that you had bunches of minor leaguers get caught.
My conclusion?
It could be anybody. Age group masters, Oly gold medal winners, national class runners. All have been caught doping so there is no way to pinpoint just based on results or times.