I switched from the OEM shocks to Rancho 9000 ones and did not see an improvement in the ride. I added an additional leaf spring on each side at the rear axle and then I saw a very big improvement.
With inadequate support from the leaf springs the shocks were not effective and this is to be expected. Shock absorbers as they are misnamed in the USA are spring dampeners that are designed to dampen the motion of the springs on a truck. It the springs are too weak for the load then there will be a lot more movement, especially when the weight of the camper shifts to one side of the truck in a turn.
I would bet that the problems with the shocks in many cases are the result of overloaded leaf springs.