Taunt should have worked fine since I looked at your achievements and you arent working on heroic. It could have been possible you had aggro and didnt know it? Maybe you were mashing buttons and your button wheel scrolled? Battle Stance? She has a curse that can lock out certain abilities. Not sure if that works on taunt/challenging shout.
However, using shield slam/revenge doesnt make a lot of sense since its likely the other tank had a huge lead in threat. It would have taken a TON of SS/revenges to catch up. In phase II, you cannot use revenge unless you are hit. Which means that you either a) had aggro or b) didnt use revenge.
You can get a glyph that will make taunt more reliable (Glyph of Taunt), but I suspect this was more a playability mistake than a taunt fail. I also looked at your spec and its one of the more unusual ones I have ever seen. I agree with what Goros said. Check the combat logs to see if your taunt missed.
Do you have an addon called Omen? Its a threat meter that tells you where you are in relation to total threat on the boss. If you taunted and you were not immediately tied with the number 1 threat holder, your taunt missed. Mocking Blow and challenging shout will not keep aggro as they do not actually increase your threat. This means that after the 6 seconds wears off, they will go back to the original threat leader with aggro. Of course, by then, your taunt should be back up so you can re-apply it.
Study the omen meter and try to figure out where you went wrong. My guess is that your taunt missed, your mocking blow/challenge shout got you aggro, but no threat (which explains the revenge proc) and it went back to the tank (or to the hunter) when the time ran out.
Deeps for show..... tank for dough.....