You may not know this but truesilver spawns in place of mithril veins at random. So really, the best spot to get truesilver is also the best spot to get mithril. I'd have to say that alterac mountains is a nice spot to get it. You have to go to the east side of the mountains near the crushridge ogres. There are 2 caves across from eachother there, the tiny cave spawns iron/mithril, the large one spawns more iron/mithril. And all around both caves spawn iron/mithril. While there I can get 40 mithril, 40 iron, lots of silk, and lots of cash in 2 hours. Outside the tiny cave is also a merchant who's been locked inside of a cage. You can use him to sell your garbage loot so you can spend more time out there.
Hyperkill - 49 Paladin
Tony - 60 Rogue