Lets be real that most, if not every UFC/Pride/WEC fighter is currently or has used PED's. I personally have pinned 2 people that have had fights in the UFC, and they were only on preliminary fight cards. Lets get real and be honest that 99% of professional athletes in all sports use some form of PED.
With that said, the very little amount of gear any of these fighters take does nothing to make them the world class fighters they are. Jon Jones would still hold belts even if every athlete was 100% drug free.
Perfect example was the TDF taking away Lance Armstrong's win. The victory was actually given to something like the 6th place rider because everyone following Lance also failed the drug test.