Ranged Haste Auras and quiver hastes (unless it's a special epic quiver that provides an aura in addition to the normal haste) always stack. A 6% haste is going to require more technology than feels to properly measure, however.
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Computing the probability that at least one of the following events will occur:
P(a or b ... or z) = 1  P(!a and !b ... and !z)
Probability
