Enchant Shield - Major Stamina vs. Block Rating

I am still using the Sha'tar shield while tanking in SSC and TK, I have passed the one from Gruul and Nightbane several times to warriors, I mainly want the one from ZA but my guild has been downing Dragonhawk 2 to 4 times a week since it opened and we have never seen the tanking shield on any of our groups, very frustrating when trying to improve that piece of gear. If there was tanking shield in SSC and TK it would be much easier with more chances for a decent upgrade.
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http://armory.worldofwarcraft.com/character-sheet.xml?r=Onyxia&n=Deadlyrabbit

Many interesting replies, thanks alot.

Yes, there are actualy three diffrent enchants for thoose who didnt know that; stamina, block rating and block value. After reading all comments I'm starting to consider block value (i.e. the enchant that makes one block more damage with the shield), rather than stamina or block rating. Aswell, I think I'll get the libram which makes SoR do more damage, seing as Libram of Repentance doesn't give much anymore

Though I wonder how many will call me a noob for having a block value enchant rather than a major stamina enchant

Since I mainly aoe tank heroics and kara on my tankadin I use the block value on the S2 shield. Ideally I'd like to get my hands on the S2 spell damage shield. I'd move my block value enchant onto that and replace my current enchant with 18 stam.

I only have 300 arena points right now so I don't know if I'd even have a chance to save up in time, and I know I won't be grinding bg's for it.