I've found that this spec works the best for my 5-man DK team. I spec just far enough into Unholy to get the Ghoul as a pet, then I go full into Blood. Also get the Glpyh of Rune Tap for a completely overpowered full-group 60% heal on a 30-second cooldown that uses only one Blood Rune! My team breezed through Outlands with that spec, and now even 80's have a hard time ganking me in Northrend. :P