I have an older (2005) 24 foot Class C on the E450 chassis and, for some reason, it has always handled pretty much like a van except for the stiff ride in the rear.
I think I just recently and finally have solved the stiff ride in the rear that we especially felt on rough highway lanes. The stock Ford OEM shocks (and other aftermarket shocks) are too stiff for highway cracks and potholes in a truck chassis, but do OK on highway curves, cross winds, and going into/out-of driveways.
I just had installed Koni FSD shocks in the rear - a nice difference. FSD shocks dynamically, in real time, adjust themselves depending on the road surface. Pricey ... but so far very much worth it.