I had one (in my signature). Had two 5.9L Cummins powered Ram/Dodge trucks before the 6.4L Hemi. I loved mine. Towed a 12k 37' 5er with it and had no issues. Plenty of power. It got 7-9 mpg when pulling the 5er. For reference, the previous 5.9L Cummins pulled the same RV at 10-12 mpg. The only downside with my 2014 (when I had it - before the divorce) was the 6 speed transmission. The gap between 1-2 was too big IMO as it would lag a bit after the shift to 2nd. The 8 speed would be a big improvement.
I towed that 5er all through the Canadian Rockies and there was very few grades that I couldn't accelerate on if I wanted to push it, never felt short of power. I CAT scaled my set up and it was about 21k combined (GCW). Mine had 4.10 gears which I would recommend.