PBL
Given that there is no such thing as an acceptable accident rate, especially to those involved, I agree that the investigators are really not going to be too interested in the A vs B issue. The 737 rudder hardovers were probably also statistically insignificant but rightly attracted massive effort (and dare one say, possibly encouraged by the location of the occurrences).
In the CGH case, I don't think anyone is suggesting that either overruns or TL mismanagement are significant issues on the millions of routine landings. The particular circumstance which is of concern is disablement of one TR and the apparent confusion caused. Try another statistic for "proportion of A320 overruns where one TR disabled" and I think you'll get a figure (at least 4 ex 7) which might suggest that action on the MEL & SB was sensible. No doubt AB's (& Boeings) will continue to overrun at a statistically insignificant rate, but hopefully no longer because of the confusion apparently caused by this particular deferred defect. Doubtless implementation will be accelerated because in this case there happpened to also be a cliff at the end of a short,wet runway.