When I lived in Port Orange, FL, WSB was very weak, but receivable during the day - on an unmodified GE SR2. I suspect that the ground conductivity at the receivers in and around Atlanta is the coverage problem, not WSB itself.
WSB was also one of the deep DX stations I got daytime in Lubbock, TX, with a large 5 foot loop (along with the Chicago clears, WCCO, and WSM). Although it took a long time to verify WSB, and there was some interference from KSEO. There are enough new 700's in Texas to wreck WLW reception, but I do have a daytime reception report from my grandfather in a letter he wrote in the 30's during WLW's 500 kW days. Reception was with a five stage tuned RF radio, that had a 28 by 20 inch loop antenna. Ground conductivity in Lubbock is very high, which would account for these extreme DX distances.
Before the new 700 came on the air in Dallas, WLW occasionally came in during the day in the winter. I suspect there were some residual atmospherics involved. I also got KOA in Dallas during the day on a fairly regular basis in the winter, but 850 was eventually covered in Dallas.
One of the things on my bucket list is to go up stone mountain in Atlanta with a good radio and a large loop, and see what sort of reception I get with virtually ZERO ground conductivity. I moved to Texas, so it may be an unrealized item on the list, but I have a collapsible 5 foot loop I can deploy quickly, that isn't insanely heavy, so next time I go that way I might do it. This 61 year old is still able to climb a bit!
With our poor ground conductivity, many of the local 50 kw AM's are noisy around power lines, and under bridges from a relatively close distance. Believe it or not, there are numerous 50 kw, non- directional AM's in the Atlanta market. WSB is obviously the only one that's 50 kw 24/7. The rest of them tend to power down to between 5,000-10,000 kw after dark, and most of them are directional after dark.
Don't think that Stone Mountain would be too great for AM DXing, but, it's super for FM DXing. It would definitely be worth the trip for that. Back in the analog TV days, it was also great for TV DXing. Haven't tried it in the digital era, but don't think it would be the same anymore.