Didn't really feel like running everywhere so I figured I'd try the Enraged Ambershards near Thunder Totem in Highmountain and waddaya know, it worked.
I farmed roughly 100 leystone an hour without any real upgrades to my mining. ~800g in trash too. Mobs are very fast spawning and the guards will help you out. Be careful of the knockback though! It will send you flying off the cliff. Easily countered by gliding with a DH.
The quest
Where Respect is Due - Quest - World of Warcraft
The mobs
Enraged Ambershard - NPC - World of Warcraft
The location