I have no experience riding past Atlanta, but go past Washington DC 3 or four times a year.
I have found coming down from PA heading for 95, its usually better to by pass DC by staying on 15, to 17, and catching 95 on the other side of DC at Fredricksburg Maryland. If it was 3AM my bypass route would add maybe half an hour, but nearly anytime in the day or evening DC traffic is stop and go, and can take hours longer.
The thing is, google maps and my GPS never suggests my bypass route - I found it myself, its mostly secondary two lane roads, but its almost always faster and far less aggravating to drive.
and here is the connection between this and your route around Atalanta: google maps and GPS is going to tell EVERYONE to take the same path, and its not going to tell anyone to take the secondary roads. When the highways are like parking lots, no one will be on the secondary roads, because the trip planners tell everyone to go the same way.
Sit down with a map and find your own way around Atlanta, or use the experience of others here, and tell the computer trip planning functions what to go do with themselves.