I've pulled with two duallys and my pin weight is 3500lbs. The first truck was a 3500 with overload springs. My current truck is a 4500 with a complete Link Air Rear suspension.
The 3500 would float over bumps similar to the ride in a Cadillac. There were times when I could feel the suspension hit the overload springs on larger bumps. When that happened there was a noticeable bump but it wasn't jarring. The overall ride was very smooth.
The 4500 with the air suspension is also smooth over bumps of any size. Over larger bumps the air system senses and adjusts the pressure automatically to overcome the bump.
Air bags may help your situation.