Pretty sure, yep. Take the raid on Silk Road 2 that was mentioned above. That same day, a bunch of darknet sites got taken offline. There were dozens of raids across I think 18 different countries.
End of the day? They had 17 arrests. And that's just arrests, so will probably result in what? Maybe 11 convictions? Police forces across the world, Europol, FBI, and the whole bit jumped up into the news spotlight and touted how hugely successful the operation was, and what a blow to the darknet it was.
I don't really know, but I have to admit, considering the size of the operation, 17 measly arrests seems like sweet fuck all. Probably cost a good $30 million in taxpayer funds, so close to $1.5 million per-arrest. I have to admit, that's pretty dismal. So yeah, I think they have a tough time tracking people via Tor. If it was easy for them, there would have been a lot more than 17 arrests.