For most tank classes the only issue with threat is in the first few seconds of the fight. It is generally not a good idea to be sacraficing mitigation, health, or avoidance for hit and expertise this early in the expansion unless interrupts are critical and they're the only ones interrupting.
1 thing i am not seeing in this whole thread is the consideration to hit and expertise. so u all know TANKS NEED A CERTAIN AMOUNT OF IT TO NOT MISS AND HOLD AGRO... simple isnt it? if i miss and dont deal damage and the dps DONT miss and keep smashing the boss then the boss will move off me.