Originally Posted by
squidbear
except 0.05% versus 0.25% would only apply if you cast 1 spell which caused identical damage every time, which has and never will happen in WoW. if you are unlucky enough to miss a 1.2million damage Chaos Bolt, or a 1.5million damage Shadowburn with Havoc up, you will lose substantially more DPS than if you had a fraction more Mastery. maybe you'll miss two Conflagrates during a fight and be down 6 stacks of Backdraft. conversely, you might never miss a single spell, or miss a single Incinerate with no spell power buffs up and not even notice. you might lose a few ticks of Rain of Fire.
RNG means you can't apply a flat % to missing hit. you either take the gamble or you don't.