I believe NW uses concourse D at ATL, which is also one of the concourses used for DL domestic flights, so the suggested/min connection times for DL intl to NW domestic shouldn't be any different than for DL intl to DL domestic.

I made a DL-DL intl-domestic connection last month, and would have missed a 1:10 connection. As RobertS975 alluded to, the main holdup was waiting for our checked bags to show up. By the time they came out the chute, which was a very long wait in itself, the lines for immigration were long. If you don't have checked bags, or your bags come off early in the process, 1:10 might be doable, but I wouldn't count on it. I'd suggest 2 hours to be safe.