When Mithril should be rare instead of Truesilver

Anyone can tell me where to farm Mithril?
I have been looking in Tanaris, Hinterlands and badlands. All i can find is Iron, Thorium and Truesilver...

Don't forget Gold, they are everywhere, even Un'Goro!

Anyways, I'd look for the Silithid hive. I found a lot of Thoriums in the hive of Un'Goro, and a lot of Mithrils in the hive of Tanaris

If you have a phobia on insect and/or oversized alien hive, yeah, I know that feel e.e