Sounds elementary, but have you checked your sway bar bushings? When I first got my coach, it swayed like a couple on the dance floor. When I checked, the rear 2 bushings were completely gone...worn out...all but melted, and the front two were hard and not flexible. I ordered new poly bushings
Poly Bushings, spent an hour or so in my driveway replacing them and wow what a difference. Still have a slight bit of body roll/sway, but I'm going to try the Cheap Handling Fix and see if that improves it. No major worries if I don't do anything after replacing the bushings. Also planning to install a Davis TruTrack bar and new Bilstein shocks.
Check your bushings and if they are original, I'll bet you'll be pleasantly surprised how much new ones will improve the handling.