Let’s dive right in, shall we?
The spec we’ll be looking at is based roughly on this one: http://mop.wowhead.com/mists-of-pandaria-talent-calculator#kMH
At 15, we’re probably going to be taking Rolling Blood. While the other two talents could be useful in some situations, Rolling Blood turns you into a dot spreading machine, perfect for simplifying aoe threat scenarios.
At 30, we have some defensive choices and the far, far away winner is Purgatory. There MIGHT be certain situations where Anti-Magic Zone is called for instead, to provide that group utility on a tough boss with a lot of spell damage flying around the raid but by and large, Purgatory is the clear winner. While there is the downside about how you need to be healed that fatal amount that would have killed you in 3 seconds, it still prevents that guaranteed fatal hit from killing you and in a raid setting, 3 seconds can go a long way for one of your healers to finish a big cast and top off your health.
At 45, I’d recommend Death’s Advance. Chilblains can be half-decent when it comes to aoe mob control in the form of slows, but in most situations, Death’s Advance’s benefits to your personal speed, as well as preventing any snares from effecting you will far outweigh anything Chilblains has to offer.
At 60, we have a pretty touch choice. I recommended Death Pact in the build for the higher burst of “oh shit” healing it can provide but a very strong case can be made for the other two talents as well. Death Siphon will probably heal you for more over the course of the fight if you use it frequently but its cost of a death rune seems a little steep. Conversion seems pretty good on paper but the over time aspect of it can be a turn-off to many who prefer their emergency heals to pack a bit more oomph right when they need it.
At 75 is another somewhat difficult choice but I’m giving the nod to Runic Empowerment here. Blood Tap’s ability to store charges and activate it when you need it can be nice, but it’ll regenerate far less runes over the course of a fight than the other two choices. Runic Corruption’s buff to rune regeneration rate is nice as it almost guarantees that you’ll have your runes activating at twice the usual speed so long as you keep attacking but I can think of more situations off-hand where Runic Empowerment’s ability to randomly fully recharge depleted runes will save your life as opposed to slowly getting back your runes more quickly over time.
The talents at 90 seem a little lackluster from a tanking standpoint. Gorefiend’s Grasp and the fact that it lets you resposition enemies will probably save more lives in your death knight tanking career than the other options but I can definitely see Desecrated Ground being almost necessary for certain encounters, so go with your gut on what you think you’d prefer.