so first off free bump
second conclusive evidence that runewords get better rolls in higher acts regardless of difficulty. i repeat:: Better rolls in ANY difficulty in ACT 5. this isnt a guarantee but for 75 runed words, and over 10 different runewords, i saw just about a 55% better roll rate in act 5 vs act 1. 25 tests in each difficulty, "cheap" and "expensive" runewords alike.
i never had a bottom 1% in any act 5, i only had 2 bottom 1% rolls, both in normal act 1, fortitude and faith (things with more than 1 thing to fail at).
not "conclusive" but making runewords in act 5 results in random stats nearly one standard deviation above the mean.