Rob,
My neighbor has that MDS 5.7L hemi and gets 35MPG hwy with his 2012. He averages high 20s in mixed driving. The most he tows with it is a trailer with 2 seadoos. Thus, all I ever see these gas sippers do is pull 'toys'. Nothing really against that, but the 1500's are too light duty.
Glad you have a 2500. I've beefed up mine to a 14,000 tow rating. My trouble was, I couldn't find a 3500 in my area, thus had to upgrade the 2500 with more leafs and run 10-ply tires. The 3500 short bed cummins is about the same for the model year too. I basically copied it.