Skyshard/Sky Crystal Farming
Solution 1:
The Shao-tien Marauders, Soul-Renders, and Stonebark Tricksters have the best chance of dropping it - about 1 in 300 chance (0.3%). There is a large cluster of these in the north of the Vale around 36, 24. If you can AoE them down... that might be your best shot.
Good luck, it'll be a hell of a grind. I'm exalted with Golden Lotus on two toons and only get one drop!