I wouldn't worry too much, there's always room for more 18th centuryists, in my opinion! The email said that I was unanimously accepted by the committee because of my interest in both the history of the book and digital humanities. My primary area of interest is in women authors and domestic fiction with regards to gendered communities, which fits in pretty perfectly with Nancy Armstrong's interests (she was my POI).
Don't lose hope yet, I think they picked me because my interests are so strongly "fitted" to Duke.