I raid on a Warrior as a tank in my guild, and I dont think that its right that Warriors and Paladins (who have shields that contibute 7000+ armor) still have less armor than DKs and Druids...
From what I have noticed is that in Naxxramas, block value was perfect for mitigating damage since the bosses in Naxx only hit for 6-10k (depending on the boss). Block Value is a very weak stat for tanks in Ulduar since the bosses hit for 2x as much as the bosses in Naxxramas, and since one block value only reduces damage when blocked by 1 (not calculating in talents and abilities)..it isnt really seen as a stat to go for...
I have 24,807 Armor value (do not have the meta that grants 2% additional armor being that I OT and am better off gemming with the meta that grants 5% block value). This much armor reduces damage taken by 61.96%. I have the Wall of Terror (off 25man KT) and it contributes 7890 armor to my total amount of armor. Upgrades out of ulduar (both 10man and 25man) only grant a small amount of armor (The Boreal Guard off 10man Hodir Hard Mode has 7960 armor; Bulwark of Algalon (endgame btw) has 8130 armor). These small upgrades of armor only mitigate a very small percentage of damage taken when hit, only add 70-240 armor, which isnt alot when calculated in with the other 23807 armor that I currently have. Since Armor isnt seen as a stat to calculate in for gear sets, warrior and paladin tanks just see it as a passive stat that comes as the gear does, and dont value it as much as other stats such as dodge/parry/hp etc...
My suggestion to Blizz is to buff the Armor Value on shields out of Ulduar so that Warriors and Pallies dont have damage spikes as bad as they currently are, and also so that warrior/paladin tanks value armor more than they currently do.
I think Block Value should remain the same that it is now (being that it would be OP for naxx/os/eoe if buffed).