I haven't seen any 05s with a frame rot problem here at my shop yet, and that's saying a lot. If something is consistently rusting out, I often see it very early.

I have seen a few late model trucks (less then 10 years old) with rear frame rot, but, so far, all of those have been backed into water for loading & unloading boat trailers. Seems the GMC & Chevy trucks that do boats have issues with the rear most crossmembers rotting through, especially the round tube above the axle and the crossmember behind that. The boat using Excursions & Explorers rot the side rails out behind the rear axle.
The only consistent frame rot issue I've seen with the Dodges is at the front where the sway bar brackets attach to the frame. Early Dakotas rust through the boxed frame near the trans crossmember, and where the channel is welded to the tube frame, under the cab.
Most frames tend to rot out from the inside out, any boxed tube frame can hold moisture and can rot out. Automotive floor boards also rot out from the inside, 95% of the time. Its caused by water sitting on top of it. That wonderful jute backing on carpet will hold moisture for 2 weeks after it gets wet once! Gene