Valid points/arguments for sure, and I agree. I'm not saying that I'm not impressed with the towing/torque/horsepower race, or that I don't support the race to the moon and back...but also that I'm perfectly happy driving my de-rated, lowly 660 lb-ft/350 HP G56 truck. Though I've read about the "torque management" these trucks have, including the manual transmission versions, my '14 2500 with G56 manual sure doesn't drive like its being held back, the seat-of-the-pants driver sensations are very satisfying (and I've owned diesel trucks since 1992, and driven diesels since 1986).
I also agree with your comments regarding medium-duty trucks...the 4500 and 5500 trucks are surely in that class (and always were), and the 3500 maybe be up there too depending on where one sets the bar, surely in towing capacity if not hauling. The GVWRs and GCWRs of modern pickups have long since surpassed the outdated classifications of "1/2 ton, 3/4 ton, and 1-ton".