The Durango is no more a crossover than the 4runner or Grand Cherokee(which it incidentally shares a platform with) ind Yes it is a unibody platform, but last I check that platform is still pretty capable vs the others. Would actually make sense to compare it with cars likes of the 4Runner, Xterra(seeing as the Pathfinder now is fwd crossover), and it's old nemesis the Explorer(though now a crossover).
Maybe... I think this is one of those vehicles that really straddle the line between SUV and crossover.
The Durango has been getting more car like over time and one can make a reasonable case that the latest generation (the one reviewed by Popular Mechanics) has become a crossover. Unibody construction, car-like driving position, road-biased handling, full-time AWD, front and rear independent suspension and finally approach and departure angles that are not particularly off-pavement friendly all point to a cross-over verdict.
Motor Trend and many other publications are calling the Durango a crossover.
That being said, contrary to most crossovers, the Durango is based on a rear wheel drive platform and delivers 6200 pounds of towing capacity. Also, although full-time AWD is standard, there is an optional transfer case that provides AWD Low (Lock), Neutral and full-time active AWD. Further, as you noted, it shares a number of drive train components with the Grand Cherokee which many people still consider an SUV - though more and more media outlets are starting to call the Grand Cherokee a crossover too! The Popular Mechanics story ends with the verdict "The best three seat crossover is not a crossover", implying that they felt the Durango was stout enough to be considered a full-on SUV; they seem to agree with your view.
Chrysler says the Durango will deliver SUV capability with crossover versatility. It sounds like they very consciously designed this as a tweener, a vehicle that at base level makes a capable crossover but that with a few options can be a satisfactory SUV. The old Durango was supposed to be the middle ground between small and large SUVs while the new one is the middle ground between crossovers and full-on SUVs. So I think it makes perfect sense that some would consider the 2011 Durango a crossover, while others might consider it an SUV.
I expect that the line between a crossover and SUV, which has always been somewhat indistinct, will continue to be blurred. Trucks and SUVs are evolving into better and better road performers while certain cars and crossovers are delivering better towing capacity, stouter drive trains and better off-road capabilities.