'99 Quad 4x4, 5.9, 3.50 gear L/S, tow package, after market Trans cooler, Auto. Tow with O/D off only. Yanking a 5000 LB boat from Jax Fl to Marathon I averaged 10.5 MPG running 65 MPH.
Have a buddy with a 2006 Nissan Titan, 5.6 L, Tow package, auto. two wheel drive. Went from Jax to maine and back yanking a 7500 Lb fith wheel. Averaged 10 MPG. Granted he has 2500 more pounds........but by design a fith wheel rig should do better on Gas milage.

So, I guess what we experience is not so bad..........

 

Yeah, but the magnum 360 is designed for constantly available low end torque, I'm not sure the Titan is. It would mean that during towing the engines would run similar, maybe better on the magnum 360, the difference is going to be when you AREN'T towing, that's the issue with Dodge, more totrque than you need, when you don't need it.

 

Your truck is 7 years older, has a bigger motor and probably weighs more ... a LOT more. Getting 10.5 towing ANYTHING behind a 5.9 is something to write home about ... especially running 3.55 gearing.