You made the right decision going with the Dually.
You can get plenty of places in a dually as you can in a single rear wheel. The place a dually doesn't shine, is deep blow sand, and deep clay mud. Single rear wheels with typical size/tread tires don't do much better there either though, so don't fret it.
The exception is Jefe's truck, with extra giant super singles, which he spent alot of time and effort acquiring. He's got the true off road truck camper vehicle of anyone here on the forum, and has taken it EVERYWHERE. If you want to know anything about true 4-bying with a truck camper, look him up. :b