Tanks do not need to reforge to hit/expertise to do this fight. Tanks do not need to alter their gear at all for this fight. Do not listen to someone who tells you this.
Tanks need to be smart about their DPS CDs. Make sure your tanks are waiting for the 'Imprint' to happen before unloading on the add. If your prot pally drops his shield right before imprint, he just wasted a shit-ton of damage. Your tanks should also be waiting for Vengeance to fully stack before popping CDs. As a Prot Pally, with all my CDs up I can land 600k Shields in my max avoidance gear. Vengeance to full + 3 HP -> Inq -> DP + AW -> Shield -> rotation. If you get lucky with procs, you can get 2 Shields in with Inq + AW for amazing crits. If I get lucky, I can solo a bird as P2 starts, otherwise with help I can be done 10 seconds early. If you are regularly behind, your tanks need to do some research.