Just for the sake of counterpoint: there are plenty of reasons that PADI standards could be unreasonably lax as to the safety of what they allow for student/professional ratios and/or acceptable environments without previously incurring enough student injuries/fatalities to move the needle as you suggest. First and foremost, PADI isn't the one with the most to lose, the instructor and/or shop providing the course are. Thus, even if PADI standards were negligently loose, the interests of those who are actively delivering the course would tend to compensate by delivering a safer course than PADI otherwise allows. Second, clueless though students are and dangerous though diving can be, most people placed in a DSD course have enough common sense and self preservation instincts to avoid the tragic outcome that happened here.
It'd only be when you have the overlap of PADI's allegedly negligent standards, a particularly lousy LDS/instructor, and a student or students sufficiently inept or unlucky, that you get a fatality. It's entirely possible that as often as the PADI courses in question are run, you just don't get that particularly alignment very often. Wouldn't change the fact that PADI standards for those classes were unreasonably unsafe, just whether your 'if they were so bad, the world would have ended by now' argument holds water.
