First build: Not bad, though grabbing Desecration is a bad choice for any specs other than PvP. You're a tank, you have to be mobile at all times (At least willing to be) and that alone negates having Desecration. Besides, the SS glyph (I highly suggest using) negates the talent as well. Other than that looks good!
Second build: This is the spec I choose to use. The cooldowns are incredible. The only thing I have different is Subversion instead of Spell Deflection. Spell Deflection only works on direct spell damage (Think Kel'Thuzad's frost bolt, Gothik's shadowbolt spam and Saphiron's breath) which makes it lackluster compared to 9% crit on Heartstrike and Obliterate. Also, in most raids the spell damage that you take is either a cone or AoE which is not mitigated by Spell Deflection.
Third build: I took one look at this, noticed no toughness and clicked out. It's NEVER worth it not to spec into toughness.
I find the only real staples of DK tanking are Blade Barrier, Imp IT, Toughness, and Anticipation. Everything else is up in the air depending on what you spec more toward (I try to balance survivability with threat gen). Fool around with the talent points until you find something that works for you. I do have to say though, you may want to seriously consider Subversion in all builds as well unless you know you're going to be MT for your raid team at all times. I know as my raid team's OT that on certain fights (Saph, Thaddius, Heigan, Anub to a small extent, Loatheb, you get the picture) I will have to dps. Its when that moment comes that your role as an Off tank really shines as we DK's have the easiest time transitioning between roles.