It is jarring, slamming and extremely harsh in that area
Leaf Springs
Leaf springs fatigue and/or can break. You won't always be able to see that either. And there is also a rubber type grommet that fails and/or moves.
Take it to a frame shop. They have the knowledge and equipment to calculate what should be on the coach and if there is a problem with existing equipment. Stay away from RV shops they don't know squat. The frame shop is also very affordably priced.
Mine was slamming also. Took it to a frame shop. They added a leaf. Rides like a limo now.
And for the front? What are you running on the front tires? I have less air in the front tires than on the duals. That is what most of us do to help the stiff ride and get better tire to ground for better handling.