Both of your counterexamples were incidents involving rider-rider collisions. There's no track design change I can think of that would've eliminated any risk of such a collision in either case. In those cases more attention is paid to the bikes and rider behavior.

On the other hand, when a rider dies due to colliding with something off track, that should be taken very seriously and the risk should be eliminated. That's one of the few things we can actually control, albeit with some compromises (circuits aren't willing to pay for changes, fans and riders don't want the course to change, etc.). To do otherwise would harken back to the dangerous old days where riders were just told to deal with it, when in fact significant improvements could easily be made.