We just purchased a new 2015 2500HD 6.0 gas and a new 2016 TT.
Dry wt on the new TT is 8375. We added 3 slide toppers and a second battery which probably brings dry wt to around 8800. When the dealer set up the hitch, TW was 1100 with nothing in the trailer.
Now that we've packed it for camping, I'm guessing we are getting close to 10,000 lbs and TW could be as high as 1300 lbs.
We've had it out 4 times so far and are satisfied with the gas. Gas mileage towing has been around 7.5 - 8.5 mpg. Power is adequate. Handling and braking is outstanding.
I don't live on the road, don't make a living with my truck, don't put a lot of mile on my truck and usually trade every 7-10 years. The gas engine meets my needs OK.