I managed to hit 120 on the death knight yesterday. I leveled mostly as frost, although found myself switching to blood for many of the harder elites. That's probably my biggest frustration with death knight leveling the last few expansions, is that frost doesn't really tend to have as much survivability as I'd like until higher gear levels, but blood just tends to be a lot slower at killing things.
The leveling time for this guy was about an hour and a half longer than it was for the hunter, which is not unexpected. The death knight came in at right at 15 hours played time, versus 13 hours and 50 minutes for the hunter.
The warfront also unlocked Horde-side yesterday, but I probably won't be able to get the death knight to 320 in time to take any meaningful advantage of it, so it'll mostly be an activity for the hunter.
Next up on the leveling front will be the paladin, which may very well have the same issues as the death knight (ret vs prot). I tend to be a little more comfortable with ret while leveling though.
I only have Champions left to get to revered before finishing up all of the requirements for this initial stage of pathfinder, and I'm working through a similar path on the alliance side in order to finish up the war campaign there and be in a position to unlock both of the allied races there.