There are significant errors
There are significant errors in the rational given on why no diesel hybrids. TRUE, the current diesel powered cars sold in the USA today only match the efficiency of gasoline powered cars. However Mercedes offers about 6 versions of a diesel powered car in the UK. Several of which provide phenomenal MPG numbers in the 60+mpg range. So a Google on Mercedes UK and check that website. Plus because of the higher torque in diesel engines their performance is better that gasoline power US cars of the same Cubic Centimeter size.
And if that isn't enough check out the VW diesel hybrid which is said to be able to get over 100 mpgs. Yes it is expensive but it illustrates that current diesel hybrid technology car provide higher MPGs. The VW diesel hybrid used all manner of exotic materials to make the car a light as possible. But using less exotic materials would not only lower the price but also still provide high MPGs in the 60+ mpg category.
I believe the real reason for the absences of a diesel hybrid is that car makers have concluded that first the EPA hassle with emissions plus the possibility of low sales are to blame.
Never understood why all other countries which have signed off on lowering air pollution all allow the sale of diesel cars.