I tend to get better results with Automobile mode but with "Avoid Highways" option set and then occasionally dragging the route or inserting a waypoint- than I do with Bicycle mode. Are you getting those dirt roads in bicycle mode or automobile mode, since I don't really get many dirt roads.
Especially with older model dedicated GPS devices. I call the bicycle modem nanny mode. It tries to avoid taking you down busy roads. Many times I have caught it taking me miles out of the way just because it thought a certain section of a road was too dangerous.
I think the best combo is:
Ride with GPS or Google Maps at home.
On tour a dedicated GPS and a tablet with CoPilot.
The dedicated GPS that I use takes AAA batteries so I never need to worry about a charge. The tablet is great for planning or looking for alternate routes while on tour.
It would be nice if Ride with GPS or Google Maps would give you auto routing based on elevation. Google Maps does give you various optional routes and you can look at the elevation gain on your own.