I've been slowly going over build after build, looking for something that suits my tanking style. so far i've found both a simple blood build and a hybrid unholy/blood build that caters to my needs; however, after going over the calculators, i seem to be doing that every few hours...probably not the healthiest of pass times, i've come up with this..
As Satorri would surely tell you, a DK tanking spec is all about synnergy Basically, you're going deep enough up frost to make Obliterate somewhat feasible. However, you are missing some key talents that make Obliterate truly worth it over going a bit deeper into unholy to pic up SS (i.e. Merciless Combat, Rime, Guile of the Gorefiend, and Tundra Stalker).
The trees are all built in such a way that they synnergize their talents to get the most out of them. The real trick to developing any tank build is to start with this question:
What exactly am I looking to get out of my talents in terms of tanking? Strong AoE, Strong single target threat, high effective health, high mitigation, high avoidance, high magic resistance, etc...? And spec to your desired playstyle/strengths.
On another side note I find the following generally weak with this spec imo outside of the lack of synnergy:
1. You specced into Runic Power Mastery....my only question is why? Assuming your rotation is tight and efficient, you should not be struggling places to find a runic power dump. This talent is, imo, mostly for blood DK's that want to extend the duration of DRW.
2. You're not specced into bladed armor. As a tank, your armor is exceptionally high and bladed armor armounts to a massive attack power boost (like 700-900 depending on gear). Point for point it is probably the best threat talent for a DK period.
3. In general you specced into a lot of increased RP generation talents but you don't have any truly good RP dumps to merit that (I could maybe see trying to increase FS's as viable but DC is somewhat underwhelming.