Simple point really. Blood DK Mastery is the only Mastery of the tanks which isn't passive in effect or practice.
Warriors - Passive Block.
Paladins - Passive Block.
Druids - Procs off auto-attacks as well as all abilities and so is passive in practice.
Death Knight - Activates only when Death Strike is used.
Passive Block is passive and unaffected by any ratings aside from Mastery.
Passive Block is passive and unaffected by any ratings aside from Mastery.
Crit shield is only reliant on Hit and Expertise values.
Death Strike is completely reliant on or subject to Hit and Expertise values, disarm effects, resource limitations and GCDs.
It's a tad ridiculous in comparison to the other Mastery functions when you consider how much the effect of our Mastery has been reduced (from nerfs to any part of the equation) since Cata launched.
The Imp Death Strike talent needs to also increase the hit chance of Death Strike by 4/8 percent and or make it an unavoidable attack against enemy NPCs. Hit and Expertise should NOT be survival stats for any tanking class (outside of Parry haste fights; which don't seem to exist anyway).
Spread the word, we can get this done.