Windwool Cloth is the Mists of Pandaria-level cloth.
This item is found on any level 85-and-above humanoids in Pandaria.
Windwool farming, while time-consuming, is easy to do. The drop rates are low, and for this reason farming medium-high HP mobs is discouraged. A good spot is the un-instanced version of Unga Ingoo if you are level 90. The Hozen there only have 214,000 HP and can rounded up in large group, then AoE'd down. Other spots include south-eastern Townlong Steppes, where the mantid there also have low HP.
As an ingredient