I'm really surprised by your empty weight also. My 2013 Ram DRW 4X4 CC Laramie weighs in at 8460 with tailgate on and tiedowns full tank of fuel but without me in it. I knew the diesels add a bunch of weight but that seems like a bunch more.
In the past the Fords were always the heaviest of the 3 or at least that has been my observation after owning all 3 brands over the years and friends weighing their rigs also. They keep raising the GVWR but they don't tell us that they raise the weight of the truck also. So you think by buying a new truck that you have increased the payload but come to find out it hardly made much difference. This happened to me when the 1999 Super Duty first came out. I bought a new dually because they raised the GVWR but when I weighed it I found out I had almost the same payload as my older truck.