I don't have a denali - but my 2011 tows like a dream. Had a 2005 3500 and traded when GM made the upgrades in 2011. My hitch weight is in the 2200 to 2400 lbs range.
I switch to Bilstein shocks at 21,000 miles and added air bags before my first tow. With my rig the rear settles about 1 3/4 inches - just touches the "over load" springs - air up the bags to about 45# and most of the sag is gone. Rides much better with the Bilstein's when towing.
My CAT scale weight:
Steer Axle - 4900 lbs
Drive Axle - 6060 lbs
Trailer Axle - 9220 lbs
Gross Weight - 20,180 lbs
2 passengers in the truck, full tank of diesel (36 gallons) and 1 small dog. Trailer is packed for 2 weeks of camping and about 1/3 tank of water.
Trailer GVWR 12,380 lbs. Add on’ s to the original weight (10,015 lbs) both propane tanks full, dual 12V batteries and 3 slide awnings.