Boots and blockage

I just joined a new guild made by some rerolls to my server and we're currently working on gearing up for T5 content. I am currently main tanking as I am the best geared tank, but my GM (a warrior) is working on his gear and I suspect he is going to want to take over once he gets a decent tanking set.

He is telling me that I need to get Blue's Greaves because I need more block rating, but everything I have read here says that they are a terrible piece of tanking equipment. My block on bosses is low ~13% without holy shield and libram (~53% pure avoidance), but I was under the impression that that is OK as long as i'm uncrushable, (esp for progression content). I do want to be able to put together a decent block set for heroics and trash and easier kara bosses but is Blue's Greaves the way to do it? Or would I be better off waiting for Jungle Stompers to drop? I currently have both Karazhan boots.

http://armorylite.com/us/The+Forgotten+Coast/tyronis

Yes, they're bad.

As long as you're uncrushable with Holy Shield, you're OK. By my calculations, you're 1.2% short from your armory. Buffs might make that up, but you should probably look into getting just a tiny bit more defense.
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Stormreaver US

Modus | Governor

If you are uncrushable the block rating they provide will do nothing for you. Since the only defensive stat those boots have is block rating, they are crap.

Most of our threat is from consecrate, holy shield has a crappy coefficient and as you get better gear (more miss/dodge/parry) it goes off less. If you want to produce more threat on trash/heroics, don't get block gear, get spell damage.
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http://armorylite.com/us/frostmane/fridmarr/

I guess what I'm confused about is why exactly Blue's Greaves suck so much. They have high armor, stam and block, and some spell damage. Aren't they good for trash? I wouldn't use them for bosses, and my uncrushablity isn't an issue (despite whatever I have on my armory I always make sure I'm uncrush before boss tanking). As long as I'm uncrittable from defense and my PvP mace couldn't these boots be useful?