I've heard the same thing about poor reliability with the new Ram Eco Diesel. Too bad. I was optimistic about it as possible replacement for my truck some day. I also heard that the 29 mpg is more wishful thinking than reality.
I've currently got a 2006 Ram 3500, 4x4, crew cab, long bed, with the 5.9L Cummins to haul cattle and other assorted ranch junk. Unloaded, on the highway, if I keep it under 2K RPM it will get 18.5 MPG at 75 MPH all day long. I can get 20 MPG if I stay around 55 MPH.
Hybrid trucks may only add 2MPH, but that's 10% improvement... so that's something.
What I want is something like the Volvo T8 XC90. Ground clearance, 14 Miles of EV range and the ability to use fuel for long drives across Texas. I could go all day on EV power puttering around the ranch and just use fuel when I need to haul stuff. But I need 12K towing minimum and an open bed to toss awkwardly shaped stuff. The first company to build a off-road, diesel-electric, locomotive with greater than 10 miles of EV range would be my next truck purchase.