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There is no doubt that calculating bitterness needs modernization. So does calculating and evaluating the rest of what hops contribute, for that matter. The mIBU calculation that has been recently introduced is an interesting one, but it still falls short of being complete, as far as I can tell. At least it says what it does, calculating the MAX hop isomerization based on given variables.
The most important thing to remember is that the origin of IBUs was to calculate values less than 50 IBU (often a lot less), as a way to interchange crop years, hop varieties and growing regions into production consistency. The needs of craft and homebrewing have completely flipped that need and made it much more art than science.
I think that any method you stick to will make bitterness predictable from your own tasting experience. It looks like mIBU is a pretty good idea towards better evaluation, but even the proponents caution that the number tells you little to nothing about bittering qualities like texture, aftertaste and astringency.