re: Don't forget how little we knew about Mars when this craft was designed
True we didn't know but that's precisely why the "poorly designed" comment has some validity. The current design made optimistic and unwarranted simplistic assumptions. A thoughtful mission that included a basic 1 meter core driller would have been more expensive and complex but would have a better shot at producing unambiguous results. Simply reflying a design from a past decade seems somewhat wastefull, given technological advances.