All I can tell you is that yes, its pretty spotty. A few years ago, when the parkway was closed around Craggie gardens, we went walking on it. In the tunnel right before the visitors center there were hundreds of monarchs hanging out. It was awesome. And of course I didn't have my camera.
If you want to try to sit and wait them out, you can try any of the overlooks south of mt. pisgah on the parkway. Heck, you might want to try calling the parkway now that I think about it, they might be able to tell you if they are seeing a lot or not.