I think Robby falls under the category of having enough experience in a Cup car along with his road course skills he was always hard to beat on a road course like Ambrose. The last couple years Robby was in the Cup Series he was running his team on a shoe string budget and wasn't competitive, but when he had the budget, or when he was driving for Childress he was always up front at Sonoma and Watkins Glen.
I think the road course ringers can still sneak in and get a win the ARCA, Nationwide or truck series, but not in Cup. Andrew Ranger has won the ARCA road course race at New Jersey Motorsport Park the last 3 years in a row, and did Nelson Piquet win a road course race in the Nationwide Series last year? The Cup drivers are just too good, and they all have road course coaches, and test at road courses. Didn't Keselowski break his foot a couple years ago testing at Road Atlanta? There's a road course race track over on the west side of Michigan by Lake Michigan called GingerMan Raceway, and I remember seeing in the media that Hendricks was there testing with Junior.