Shocks, with the exception of air shocks or air bags, are not designed to carry the weight of your vehicle. That's what springs or air bags are for. Shocks are there to control the "spring action" of your leaf or coil springs. I'm sure you've seen old vehicles bouncing up and down as they navigate down the road, they need NEW SHOCKS!
The recommendation of new spring and shocks is a solid recommendation. The alternative would be air shocks or air bags to supplement your current rear springs.
Myself, if the OEM suspension is adequate to handle the weight your putting on the rear of your vehicle, I'd replace the springs and shocks. If that weight is at or close to the max weight your vehicle can handle, consider air shocks or air bags.
Days camping (2015)----88 days
Days camping (2016) ---110 days
2016 Wildcat MAXX 28RKX (33' TT), 2007 13' Scamp
2015 Ram Laramie Hemi
30 years RV'ing
12 different RV's