That's a rather old paper though, it's 8 years old and I could have sworn that it was shown to not be effective in detecting current TOR traffic. From what I understand, you have to have massive traffic shaping capabilities to even begin to "chip away", just not a viable nor efficient solution as it takes huge resources. They're not going to devote that amount of time and money just to shut down a few nefarious drug resellers or other places.