When I had my 2004 Ram 2500 there was (and currently still is for that generation of trucks) a huge issue called "Death Wobble" This was only an issue on the 4x4 models with the live front axel. Basically due to either tires, miss-aligned suspension, shocks, or a combination of all, you would get a very violent vibration after hitting a rough patch on the road which would not go away until speed was decreased. This is a good video of it below;
I bring this up because its sort of similar to what we are currently experiencing. Dodge would balance tires, re-align suspension, etc, basically cover all its bases and still some people could not sort it out. Others found that certain brands of tires would be more prone to death wobble, so members on the forums were urged to replace those tires first. I remember the original BfGoodrich KO's were known to cause death wobble.
I think in our case the Goodyear tires seem to be causing issues. Although a member up top did say he experienced vibrations while on the stock Continental tires as well. Do users on the 18" wheels also experience vibrations? It would greatly help is users would post the basics of their trucks when posting complaints. Things such as year, make, model, cabin type, engine, rear end, suspension package, milage, wheel size, are all important factors to keep track of. Who knows, we might find that z60 packages are more prone to this or vice versa.