I try to a little thorycrafting, but I am no expert. However by looking into ask mr.robot then testing it on my own toon I realize that when I proritize Hit/Exp i actually have a higher mastery % than if i prioritize Mastery itself! I give up about 5000 health and 3.2% avoidance, but i gain 6% DPS increase.
As a side effect of hitting more you build up more of the mastery bone shield so the mastery effect is even bigger. Why isn't there more hit/exp dominant blood DK? What am i missing?
my toon as reference us.battle.net/wow/en/character/dalvengyr/Killerbush/simple