The gross numbers of failures aren't going to tell you nearly as much as numbers by type of torpedoe and type of exploder and where and when ( magnetic back ground noise and sea states in particular) all added together. Your trying to apply data principes at an inappropriate level and it will drive you crazy because you are measuring the wrong things. There have already been significant discussions on the various TDC, is was and other fire control equipment within this archieve. There were significant CO failures in the USN early in WWII. There were also equipment failures when some sub CO's were given general blame for when they did as good ahumanly possible.
Generalizations always have exceptions and generally are a disservice to understanding.