All engineered products, whether it is a diesel engine or a suspension bridge, are designed with a set of goals. The bottom line is cost. Anyone can build a bridge. The idea is to build a bridge that will just barely not fall down or in this case, an engine that will meet power and longevity goals without blowing up for the lowest cost.
All the components are designed to work within and achieve the designs overall goals. If rod bolts are a failure point, stronger bolts will only expose the next weak point, and so on. Once you are past changing a bolt, other changes likely become too expensive or difficult.
If you keep in mind the limits of the design, I doubt that there are serious faults in the design of the LDx series engines. For catastrophic failures, I would be more suspect of the assembly process and/or component quality used during assembly, or operation outside of design limits.