Bark, please reveal the secrets of successfully playing a Blood DK unto me. I want to try something other than Prot tanking and I have sadly been puzzling over this for some time. Please rescue me from my dilemma with your superior knowledge.

Stack mastery, keep diseases up on your target(s) at all times, rune strike to dump RP/generate threat.  Death Strike is your new best friend. You can either use it to build up a large blood shield, which absorbs incoming damage, or to heal yourself after you receive a large amount of damage (blood shield is a function of incoming healing and mastery which is why we have ridiculous amounts of it.)