Embersilk Cloth is the Cataclysm level cloth, found on humanoids level 80 and above, mostly in Cataclysm zones.
You can also buy Embersilk Cloth from Honor/Justice Point vendors,
Before you start farming, go to the Auction House and buy a [Potion of Treasure Finding] or make one for yourself if you are an Alchemist. With this potion you gain the chance of looting [Tiny Treasure Chest] which contain Embersilk, Volatiles, and gold. Gold is a guaranteed drop, while the other two just have a high drop chance.
[Northern Cloth Scavenging] also works on Cataclysm mobs if you have Tailoring 400. This means Tailors will get a lot more cloth, the drop rate is horrible for non-Tailors.
Embersilk Cloth in Tol Barad
In my opinion the best place to farm this is Tol Barad, the Restless Front. You will see the Restless Soldier and Restless Infantry bash each other to 19k health, which means it is easy to kill them. The respawn rate is high, you will never run out of them.
I'd like to add that not every mob drops Cloth, and I've seen some drop 4 and some drop 1.
Embersilk Cloth in Deepholm
This is a really good place for anyone that can do okay AoE. There is a battle going on between Dwarves and Stone Troggs, so most mobs will already be damaged and they are in pack of 5-8.
I do not recommend this place if you are not a Tailor or if you don't have the Treasure Finding potion, but this is an excellent place if you have both.
Embersilk Cloth in Twilight Highlands
The Twilight Gate in Twilight Highlands is also a really good place to farm Embersilk Cloth. Start killing Twilight Ettin, Bloodeye Magelord and Bloodeye Brute. These guys hit hard, don't pull too many of them.embersilk cloth, instance drops embersilk, wow farm embersilk, WOW FARMING EMBERSILK