If people think the NSA isn't all over the dark web, they be dummies.
The NSA isn't that concerned with where you buy your pot. They aren't even that concerned with where the local gangbanger buys his guns, or where the local perv sources his kiddie porn.
If you're going to wear the tin foil hat at least direct it at the appropriate three letter agencies: FBI, DEA, ATF, et. al.