http://www.tentonhammer.com/node/32704
Pretty good info. Confirms some things about simply requiring a level 55 character on any server to unlock one DK per server on all servers, DKs being able to be any class, and the rune system. Apparently, their tanking niche is going to be as an anti-caster tank (like the Inquisitor was supposed to be in Vanguard). It will probably destroy casters in PvP too, with the ability to teleport things right to its feet. I'll probably end up having to level one, what with already having a 70 prot war, 70 prot pally, and up-and-coming 62 druid.