Embersilk Cloth Farming in Twilight Highlands (Glopgut's Hollow)
One of the best places I've found to farm for Embersilk Cloth is Glopgut's Hollow in Twilight Highlands. Glopgut's Hollow can be found just north of The Gullet, a small Horde town and just west of Thundermar, an Alliance town. Here you will find Glopgut Ogres that have roughly a 50% chance to drop anywhere from one to three Embersilk Cloth per kill. There are quite a few ogres here and the spawn time for them seems to be roughly 1 minute. It seems that only Horde have quests for the ogres here making it less likely to be over crowded depending on what the population ratio is on your server.
The only downside I've come across in this location is the ogres are all extremely spread out. About five or so spawn and patrol outside, the best chance of finding an ogre here is inside one of the buildings. Keep in mind that a lot of the buildings here have second floors where more ogres can spawn, so check them out too!
Embersilk Cloth Farming Video: