Really? There's a high spawn rate for Wonder Rocks in that area? I've only seen two or three, I think. One or two I saw on Emerald Mountain, (I got the Lumicite, but I don't think I beat them...) Then I saw one in that spot but I fell down the slope before I could fight it. :(
I find it's much more time-efficent to simply grind Red Ghaj in the Present Vortex, though. You need to spend about 5 minutes or so to get a Wonder Rock to spawn, yet in that time, you can get about twice as much exp or so from Red Ghaj, which are guaranteed to spawn...