I'm trying to get a new version of the guide stickied (one that is posted from my new server/guild), so if you could please request that the sticky be swapped for this thread: http://us.battle.net/wow/en/forum/topic/7416264606
This guide will assume you know the basics of the class (basically anything you could get from a tool tip). It is written with lvl 90 tanking in mind and while the information could be useful at any level, it is not made with leveling in mind.
3) Stats (Gems, chants, ect.)
4) Playstyle ("rotation")
5) Advanced Playstyle
6) DK specific encounter guides
The new talent system for Mists is designed to be more fluid, but there are still better options both overall and for certain circumstances. I'll provide some standard spec builds, but keep in mind with this more fluid system you will find yourself tweaking a lot more often.
5 man spec:
stable build that has a focus on trash pulls and aoe threat.
Challenge mode spec:
Similar to the 5 man spec, but made for fast chain pulling through large groups of trash as well as some add control options.
Single Target raid spec:
focuses on survivability. the basic "mechanic neutral" raid tanking spec.
AoE raid spec:
Focuses on add control with lots of weak adds in mind.
Because of the more fluid nature of talents in MoP there is a high chance that you will need to tweak any of the above specs to be 100% optimal for a specific situation. Because of this, I'll give a run down on each tier individually and how you would adjust the above specs in practice.