You mean like this?

Quote Originally Posted by Ghostcrawler
Unholy Aura was becoming mandatory as a raid buff. We considered giving it to other classes, but realized we would just be accepting all players moving faster all the time (which subsequently also makes some boot enchants look bad). Frost Aura was kind of lame, but I'm sure we could have come up with something better. Mostly, the mechanic was just a little awkward and hard to explain. We like the new one better.

Players often wish for a buff so awesome that it guarantees them a raid slot. But that is exactly the mentality we were trying to prevent with our big buff and debuff overhaul. In the Sunwell era, raid slots were already so precious that there is a good chance a DK might not have even earned a spot, and having more than one would be a total waste... unless we gave them two mandatory buffs, in which case the Retadin, Boomkin or dps warrior might have gotten the heave ho.

The new model is designed to let you get as many buffs as you want through several different configurations of classes and specs and still have some slots left over to bring who you want.
Sounds like blood DKs are screwed, however it didnt specifically mention blood aura above, so I hold out some small hope...