DuckDuckGo isn't a search engine for Tor, it just provides a hidden service interface to its regular search engine. If you want to make a hidden service to help improve the overall quality, let me know and I can help you get it all setup.
Though writing this gave me an idea: is there a .onion Torrent index?
edit: fixed Tor capitalization
Beyond that, I think that dedicated TOR users will shy away from using BitTorrent since it's a huge privacy risk. They're more likely to be using FreeNet or I2P for anonymous P2P filesharing.
It is The Pirate Bay