Quick answer is yes, many are over weight. Hopefully, safely. My rig is about 500# over the door sticker on the rear axle. The axle can carry the weight so the the weak point is the tires, springs, and shocks. My door sticker rear axle weight specifies 6200# which is the rating of the tires. My rear axle weight with the two of us in the truck and 20 gallons of water is 6400#. To compensate I kept the factory 16" steels wheels and put on tires rated at 3750# each and air springs.
Another thing to consider is that I'm running a gas burner and the whole truck (CC LB)with the wife and I both, no camper, weighs only 6200#.
The tires are the safety factor, so don't exceed their max.
Your going to get many opinions on this so you'll need to sort out the math.
If I could get the wife to leave her purse at home we could carry a lot more.
Good luck,