I haven't had a problem with my 5ver and our 4WD. I have frequently switched to 4WD when driving across problematic land, thru big puddles for example.
However I don't think 5vers are better than TT for rough roads. The best for that sort of driving would be Truck bed campers and maybe Class C campers. Ground clearance and solid construction are big pluses for that sort of driving. The RV will get a real shaking and it will test all those welds in your Lippert frame.
Tho we do as much back country exploring as possible we prefer to leave our 5ver in a CG near by and do the exploring in the truck.