That spec just doesn't seem good... at all.
Blood of the North and Guile of Gorefiend are two AWESOME talents.
You don't want Hungering Cold.
You do want Glacier Rot.
You don't have much use for Runic Power Mastery. You should be using Rune Strike and Frost Strike way too often to make use of an extra 30 RP.
Icy Reach isn't that useful to a non-PvP DK. You will always be in melee range, other than pulling, and you can Death Grip to do that.
Killing Machine > Deathchill, even at one point. Killing Machine 5/5 will have you critting ALL THE TIME, even as a tank.
Subversion 3/3 should be a pretty nice threat boost.
Morbidity just ISN'T a good talent once you get the hand of multi-target threat control. And, even then, you should only need 2 points into it. Runes refresh every 8-10 seconds. You will want to refresh diseases every 20-21 seconds. So, basically, you will have a rotation of diseases+Pest/BB+DnD and then a rotation of HB/Oblit and BB (or, better, pest on two mobs to refresh all diseases, so you can Oblit or HB instead next rotation)*2.
Acclimation is situationally useful. Some instances it will be very, others it will be little. It is up to you whether or not you always want to spec it or just take it when needed.
[EDIT]
Final note, why the hell are you taking Lichborne? It sucks for tanking now...
Your second build doesn't seem much better.
Morbidity without Epidemic is just stupid. That means you will just have a horrible rotation, often without diseases (destroying your HB and Oblit damage, which you will almost never be using).
Why aren't you taking Annihilation?
There is just so much wrong with the build. It makes no sense from an AoE, single-target or mitigation perspective.
Look at this one:
Frost Tank Build It would be best if you could run with a shaman, letting you drop a full 6 points. Add 3 to KM, and put 3 in Acclimation.
And then you have a much better build. If you will be doing a lot of DnD, you can put 2-3 points in Morbidity and 0-1 in Acclimation or, if you really want, Deathchill (and, even then, just for the rare case you won't have a KB available to crit your first HB for threat).
Edited, Mar 19th 2009 6:17pm by idiggory