It seems that I remember seeing many complaints about this on these trucks in various places on the internet.
There are lots of complaints. When you boil it all down, the complaints revolve around a lack of information, crappy dealers, and unqualified people trying to fix them with hammers.
If they are repaired correctly and problems aren't ignored, they run for a long time. There are several Hino-only fleets that utilize my shop, and the trucks are replaced with more Hinos when they are wrecked. The occasional engine gets rebuilt instead of retiring the truck, and blown up transmissions are replaced and the truck keeps rolling.
They are good trucks when taken care of, imo. We've run some numbers and the total cost of the vehicle plus repairs over a normal lifespan is lower than on a few much more popular brands.