Admittedly I'm not well versed in TOR and how secure it actually is but surely it would be more actionable for major intelligence agencies to operate a number nodes in the network and use them to attempt to track and mitm requests?
As for encryption I haven't seen much to indicate a deterrence strategy, but maybe I'm not following the media as much as I should.
"Current: access to very few nodes. Success rate negligible because all three Tor nodes in the circuit have to be in the set of nodes we have access to"
It seems to me that the two tactics could be complementary. If you discourage people from using Tor, then you don't have to devote as many resources to the people that use Tor.
As for encryption I haven't seen much to indicate a deterrence strategy, but maybe I'm not following the media as much as I should.