In a sense, we already have a fair qualitative idea of what kills pilots - flying into IMC; carb icing; engine failure at night; the impossible turn etc... One could also argue that it doesn't really make sense to worry too much about the proportions of most of those accidents, because whichever one we neglect is the one that will catch us out. One has to think about all of them.
The 'killing zone' asks a much more general question - what the time course of developing a reasonable general level of competence and judgement is. The problem it tries to address isn't so much people doing demanding and risky things, as people doing risky or stupid things through ignorance rather than intent.