Rightio, First off Taunt consists of two parts, it brings your threat to equal that of the current aggro holder of the target, and second it forces the target to attack you for a few seconds. Since on the pull you are liable to be the aggro holder it does bugger all for your threat, though it does force the boss to keep attacking you for the first few seconds.
The Max threat Rotation is
Shield Slam >fish >fish >truck
which you restart each time Sword and board procs
Fish is either Devastate or revenge, Devastate is superior Single target threat to revenge. Revenge is only worth it if you need to save the rage.
Truck are Shockwave, concusion Blow, and Heroic throw. Concussion Blow is the greatest of the three and Shockwave only really cataches up to Heroic throw once vengence has started stacking.
of course at the same time you still burn excess rage with the appropriate dumps, Using IR frequently as can be permitted, while keeping your debuffs up and interupting and reflecting as necassary.
Opening Threat is a prot warrior issue, generally popping a golem blood potion and retaliation prepull help, add recklessness in if you don't think the extra damage taken is a concern. Your Max Threat Opener should be exactly the same, except with the caveat that should break the rotation to burn Concussion blow while Recklessness and golem blood are up, and you pop Zerker rage, and shield block as you charge.
Your Spec is missing out on some night vital threat talents. You do not need Blitz. Gag order, Safeguard, Imp.Revenge, Blood&Thunder, and Thunderstruck are all quite situational. You Really should pickup Heavy Repercussions and War academy, Polishing off Incite and Deep wounds are also be great (both are more threat than cruelty).
Not threat related, but the Eternal Meta is superior damage reduction for prot warriors over the austere.