Most current mechanics I find rather interesting.
I actually somewhat hope that we don't get more defensive cooldowns moved over because that'd just mean the individual ones get weaker. And I enjoy VB the way it is, it's quite fitting into the blood theme and powerful enough, with a useful but not 100% necessary glyph.
Again, I think this works. Including it's extra talent and the glyph. It saved my life plenty so far, the only thing I'd maybe change is to exempt it from causing Healing Absorbtion or it could end up too strong given the new healing setup in Cata.
Most non-tanking talents
Well the question with these is: How are they going to stay in Cata? And if not, will we get replacements + a serious nerf to Frost Presence so we have to pick all those new tanking talents up? But hrm... passive talents are to be removed, so they can't do that either.
In any case, I don't have an issue with these ofc. Threat talents are threat talents, one hardly notices them.
Now the talents I think could use some work:
Improved Blood Presence
This is interesting although ofc useless if Blood becomes the tanking presence and then needs a change anyways.
If it stays as it currently is (Frost for tanking), then this would ideally need some buff to how much health one drains. I like the idea of a small non-saving but near permanent HoT on me, it's just too small right now.
These could use a similar treatment, currently mine heal for 400-800 health every 2s in a raid (total), which is just way little.
An interesting idea here would be to move DRW down the tree and make active Bloodworms on a 60s cooldown the final ability, but make them drain a significant amount of health.
Dancing Rune Weapon
Hrm... while I know it transfers threat, it's still extremel misplaced. Lower talent position, mebbeh.
Will of the Necropolis
I think this is too strong, but I know I'll not make friends with saying that. However I do think that sometimes talents should be held against an arbitrary scale too, and for a single talent this has a lot of power. It should be weaker while the DK tanking as a whole should be stronger.
As for it's general cycle, like Frost and Unholy always have a choice to use Death Strike instead of Obl/SS to get some health back in, we need a similar choice not to use DS, or even better when to use Blood Strike over Heart Strike again. Some choice to soften up the rotation.
-- (The Death of Rats, Terry Pratchett, Soul Music)