Skipness 1E; I agree with your comments about the ATL flight's late departure time (13:45 ISTR) and the consequence was a very late arrival time of onward connections. DL's JFK connections weren't great either, often requiring a change of airport to LGA and/or a five or seven hour layover. As with ATL, the arrival time of the onward connection was invariably far too late for me.
Connections via EWR/LHR/AMS/LGW were always far superior for my journeys, with the result that I never used either of DL's services from EDI. This was a shame as I really would have liked to have supported the routes.