This is why I change VPN providers every week, use a hardened up Whonix with physical stream isolation and also keep changing location, I never use my home connection for any Tor business and the connections I do use would be incredibly hard to trace, assuming of course they control any nodes I use since I maintain a massive node blacklist to prevent snoopers. Furthermore, I have tried recently toying with the idea of Tor over Tor, much like how SilkRoad marketplace itself runs. The DDOS attack didn't hit SilkRoad servers but rather hit the RV points in the network if I am correct, so by doing Tor over tor this allows you to not reveal the introductory points or RV points so easily. The danger being though, your end exit node being the same as the entry one, but you can modify your torrc file to counter this.