Who knows? Nobody. The drug question comes up in every sport. Just like the cyclist that had cancer. He is kickin butt so he must be on the juice people say. I know people that are very clean and are monsters. We can't really judge by the numbers in all cases. I give respect to all lifters pushing their bodies and mind to the limit on the platform.
People like them are insanely strong no matter what. Steroids does not make a lifter world class. Coan and Garry Frank have been strong for a long time. Coan was breaking records as a high school kid and Frank was pro football. I have spoke to Garry on the phone a few times and I know these world class athletes have lived strength virtually their whole life. Drugs or not they are doing what nobody else could or can.
To answer your question there is no way to tell how prevalent steroids or any other drugs are in the sport. It is impossible, at this time, to get an honest count or survey. Anybody with a quote is simply guessing.
Train hard and train smart.