Long title huh? One of my two favorite farming spots thus far in MoP is just outside the Pools of Purity and The Heartland in Valley of The Four Winds. Don't forget the Golden Lotus too! I am averaging one node per 30 minutes atm, and as many stacks as I can carry of the others.
You knew it wouldn't be too long? For the last couple hours, I have had zero competition in this little area, so I have been hanging tough.
Basically, Start running. You can see on my map above that the majority of Ghost Iron is on the waters edge, and the herbs (Green Tea Leaf, Silkweed and Golden Lotus nodes are around the little Panda farm).
And with the Gathermate setup (addon), you can see how packed these nodes are.
It takes a whole 5 minutes to do a run-around the little circle, and by the time you are back at square one, you are ready with re-spawns....
If you do get competition, which will happen sooner or later, there are a ton of fishable pools that are in the area as well....ok, maybe not a ton, but there are six that I have counted.
Good luck and happy farming folks!