John arrrived in Coschocton County at the same time as George Allabaugh. There is reason to think he married George's daughter Maria before that. See George Alabaugh of Crawford Township, Coshocton County, Ohio.
Since George had arrived in Ohio from Washington County, Pennsylvania, I looked there for likely Dial families of which John might have been a part.
There were no Dials in Cross Creek Twp, Washington County, but I found Thomas Dial in neighboring Hopewell Township with a large family that included a son born between 1800 and 1810. Could "our" John have moved out of this household? John named his first son Thomas.
There was also a Simon Doal in Hopewell Twp, but he was too young to be John Dial's father. There was a Joshua Dile in Smith Twp, but he was in Buffalo Township, Fayette County, with no children in 1820.
But where was Thomas before that? I did not find a match for him in 1810 or 1820 in Pennsylvania or Virginia.
I used this site as a starting point for Doyle family, including for the sons of Edward Doyle II in Bullskin Township, Fayette County, Pennsylvania: Turner Genealogy.
The following resources, which I did not have access to, might provide more information on John Dial:
Violet Dial DeMoure (Compiler), The early Pennsylvania Dials-their ancestors and descendents, 1972
Dean Alexander Doyal, Descendants of Edward Doyle Sr (1700-1741) and Priscilla Connell, Newport News, Virginia, 1995, available at the Allen County Public Libary, the Family History Libary in Salt Lake City, Utah, and a few other places.