It's not just a matter of towing up a hill. It is acceleration from a standing start, acceleration during passing moves, start and stop driving - regeneration issues, servicing costs, etc. Basically the day to day life of light duty trucks.
So my comment on LD diesel engines devolving is based on this. The gas engine is getting so good, and the perceptions of diesel advantage is not realized in the light duty market except in very limited use type cases. If you look at diesel engines in the world market, the pinnacle of LD diesel was the last generation of common rail. That engine had the same advantage/disadvantage as it's HD brother.
If you look at the current and developing HD market, diesel is a much more clearly defined advantage/disadvantage. The light duty market in comparison is ambiguous. Give it about three more years, and I think we'll see a more clear direction.