Interesting. I wonder whether there is something I am not accounting for? I do not have access to the Legion alpha, therefore I am working strictly on theoretical level. The equation I am using is as described in
this Wolfram Alpha link (please ignore the graphs, Wolfram Alpha shows them over a completely useless range), or on
this google docs sheet - please ignore the last two pages, they are a work in progress x) (and not relevant to this discussion anyway)
In the Wolfram Alpha link, x stands for haste percentage, y for crit percentage and z for absolute value for overtime coverage. The first part of the equation (the two multiplied fractions) stand for Judgement crits, the second part stands for SotR charge regen.
In the google document, I am using the equation a bit "bigger", although it is equivalent to the one on Wolfram Alpha; it just stems from the original thought put into mathematics, before the equations were simplified (as they were still equivalent, and me being lazy, I just left them the way they are).
(sidenote - I hope the google sheet will work, considering that local (Czech) decimal notation uses a comma instead of a period to separate integer part of the number from the rest)