We had a 2004 2500 LB7 Duramax. Plenty of power in the mountains but the transmission cooling system was too small. Overheating problems.
The 2006 2500 LBZ Duramax has a larger cooling system for the engine and transmission. Now, we do not have the overheating problems we had before. Pulling in the mountains does require a person to use common sense. We try NOT to pull during the hottest part of the day because it is hard on the engine, transmission, and tires.
Being at or slightly over weight capacity can be debated until the end of time. But we never hear anyone ask 'when did you last adjust the trailer brakes?' We adjust our trailer brakes every 5,000 miles.
In our opinion, a person needs to use common sense when driving down the road pulling several tons of weight.