WoWDB

It took me about two weeks of camping to get this guy. I had four characters from different servers camped at both silithid areas in Tanaris and would log over to see if a sandstorm was up. I logged in during a number of in-progress sandstorms, but never seemed to be around at the start. A few things I found:

1. They do not spawn inside the tunnels (I felt silly asking this the first time, but I figured others might have the same question), only on the surface.
2. They do not respawn during the duration of the storm (others mentioned they do very slowly, but I've sat through an hour/two-hour storm with no greens paws).
3. You HAVE to be there at the start of the storm since only a few spawn at the start. (Edit: Maybe they now respawn during the duration of the storm, based on Funky303's experience. This would be AWESOME.)

I decided to stay on just a few minutes longer while I went to get ready for bed with no storm up - came back 5 minutes later with a storm and 3 green paws on my map (I was at Gaping Chasm). I caught my first one, and when the battle was finished, the other paws were already gone.