Many moons ago Kuren started talking to me about the blood shield mechanic for deathknight master introduced in Cataclysm. I became interested in the mathematics of the problem, and at least at the time, some of the then-current mathematical ideas about stacking mastery or avoidance were... well, completely wrong. More precisely, they assumed no blood shield would ever be absorbed in the 5 second before the next death strike, and that just isn't even close to true. Anyway, I derived some formulas back in February for optimizing mastery and avoidance stats, and it would seem a waste not to use puts those formulas to use. So I made a spreadsheet and a webpage that allows you to enter in various stats and then tells you how good avoidance and mastery stats would be for you. It's posted on a new page, here. Let me know if you see any issues with it.