Needed - Statistics on Runes

[Samka]

Chances of getting anything higher than Vex, from anywhere in the game, are incredibly low. Drop calculators have odds on these, but I'm disinclined to believe them simply on the basis that the rare runes seem to drop more often than they would indicate. They are still unbelievably hard to find.

Vex and below can be reliably retrieved from the 1-player Hell Countess if you're willing to run her enough.

Hellforge rushing and then cubing is an option for high level runes if you have a good buddy.