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As a trend, what I see as the number of targets, n, increases, then the rough estimate value of the stats is something like
Haste = 3+1.25n
Mastery = 2+1.5n
Crit = 3+n
(Those numbers aren't exact, but give a rough estimate of what I'm trying to get across if you think mathematically best)
That is, up until 5 targets Haste is very, very good. Past that Mastery scales up in value a ton. Crit is about equal to Haste, but falls behind the other stats with more Haste.
Single target Haste/Crit is very similar, with 2-4 cleave Haste is very, very good. Past that Mastery scales best.