Use a better PRNG unless OpenSSL starts using a better one on their own.
#17694 (moved) hashes important PRNG output with some system randomness before use, so that observed PRNG outputs are resistant to PRNG state analysis.
But almost all of Tor's use of PRNG outputs is observable from one or more locations outside Tor, whether in salts or nonces sent to other machines on the wire, or in the random choices made in guard, directory, and path selection.
We could hash all of the bytes coming from the PRNG to avoid this state exposure. (Although we might not need to use the system randomness source each time.)