As a bear tank, I use all Frienzied Regeneration, Barkskin and Survival Instincts to take impales. The rotation we use for tanking puts me (in order of impales to platform) 2-1-1-2, and on the 2nd platform I need a pain suppression, as I only have barkskin off cooldown at that point. Don't be afraid of using stamina trinkets if you need the extra health to survive the impales, dodge will not help you in any way on this fight, as both Impale and Tetanus are unavoidable, and the only two threats to a tank in this fight.
This is assuming you're in 25m and have access to raid cooldowns.
Also, Mirror's overrated, I never bought it at all in this expansion, and not once did I hinder my guild through deaths that wouldn't have happened had I had the trinket. All spell damage to tanks this expansion is highly predictable, and unlikely to kill a tank by itself. Your healers should really be watching timers and pre-casting heals better.