I've been stranded twice in a 300tdi, once due to an injector pipe fracturing, then another due to a water pump. A water pump is something you could carry as a spare, but I doubt you would get a #3 injector pipe and carry that as a spare.
I think that with a proper risk analysis you will find that the common rail is more reliable than a mechanical system, fewer moving parts. Yes I agree that cr's are are dependent on good fuel, but you would be crazy not to prepare with proper secondary filters etc.

