Well, one thing that I'm pretty sure happens with those damage ranges is that if the rounding is a .51 --> 1 or .49 --> 0 kind of situation, you will need a *lot* of tries to even see it happen. Pretty much why I take a mishmash of potencies (and include crits as x1.5 potency) when I test damage values; yeah, it's making assumptions that that's how it works, but in practice it makes that sort of thing less of a problem.