ALLIANCE ONLY
Sorry if this is a repost of some kind, I searched the forums for a few minutes and could find nothing.
First of all requires, to do this, you must not have completed the quest "Siege Tank Rescue" in the early part of Twilight Highlands. This quest is part of the quest chain that opens up the portal back to Stormwind from Highbank in Twilight Highlands.
This quest has you defend a siege tank from a few waves of attackers. These attack waves consist of 1-2 Axebite Grunts for a total of around 5-6 Axebite Grunts. These mobs have a great drop chance on Embersilk Cloth (47% according to Wowhead although the drop chance was significantly higher for me). The thing that makes this so viable is that these mobs only have 16k health compared to the 70k+ health of everything else in Twilight Highlands.
The process:
1. Pick up the quest "Siege Tank Rescue" from Fargo Flintlocke (77.0 , 69.9).
2. Talk to the Siege Tank Commander sitting on top of one of the siege tanks North / Northeast of the questgiver.
3. Kill the incoming Axebite Grunts and loot them - Be quick with the looting though because the grunts have a relatively quick despawn timer on their corpses.
4. Abandon the quest.
5. Repeat
6. Profit $$$
If this isn't viable or isn't clear enough let me know as this is my first time writing a guide.
Quest: http://www.wowhead.com/quest=27468
Mob: http://www.wowhead.com/npc=45187