Spoon, I think we agree; for the most part anyway.
Think of this. You say you want more efficiency. But then you say that "most" people want more power. As Joe Dirt would say: "It's not about you brutha; it's about the CONSUME-Aaaa." You want Snakes and sparklers. :B
GM or Ford or Ram or whoever is just following the money trail. If the consumer wants power they are going to give them power. "When" the consumer wants economy, that's what they will give them.
Remember in 70 when we had 450 HP 454's? Then in 72 we had the Vega? LOL. What changed? When the gas crisis hit and gas tripled and then some, the CONSUMER changed!
A friend has a 1969 427 tri-power Vett. When the gas thing hit he traded it straight across for a Dotson pickup!!! He had to get to work and he couldn't do that with the Vett.
The bottom line is this: If you own a diesel and want better fuel economy just keep your foot out of it and you will get better fuel economy. You want better fuel economy, buy a more aero trailer like a hi-lo or pop up. Or buy an eco-diesel.
You also can get a de-tuner just like a tuner. My friend did this with his Volvo tractor he tows with. He detuned it to 350 HP because he could not control his right foot. Now it only puts out 350 HP (and fuel through the engine) no matter how much he pushes his right foot down.
Much like my 6,000 lb 5.7 diesel caddie can only use 105 HP worth of fuel. That's why a car as big and heavy as the Titanic and get and honest 30 MPG out on the highway! :E
The only thing I wish the big three would offer on their diesel pickups is a Eco/Power tuner. You just be boppin around solo? You can put you tune on Eco. If you are towing, you can put your tune on power. The problem with that is government regulation.