To be honest there is enough mastery on everything else to make the cape, at least, worth getting. Beth'tilak (can) drop a sword, you get a belt with over 300 mastery rating on it from shannox...
I would stick with a mastery trinket + symbiotic worm until you have enough block that your Worm procc puts you way over 102.4%. Then either take the moonwell phial (I don't like it because you can't move more than 10 yards for 20 seconds if you don't want to lose the dodge boost), the scales of life (not a big fan of the /use but I guess 19k heal (it scales with divinity) every 60 seconds isn't too bad, or the trinket from V&T (n-hc or hc).
Mastery is awesome, but if you reforge the correct stat (i.e. not always the hit or expertise) you can get an item with 55 stamina, 25 strength, more avoidance and nearly as much mastery. Look at this item comparison:
I would use the 378 unless the 37 mastery rating was the difference between block cap or not. You gain 55 stamina (about 800 hp), 70 armor, 137 parry rating (about 0.6%) and 115 hit rating (~1%). You lose 17 strength (~3 parry rating), 37 mastery(0.4% block) and 127 dodge rating(about 0.5%). Just because mastery is out best stat doesn't mean it exists in a vacuum and and item without it is crap.
How likely are you to get the beth'tilak sword? I replaced the weapon I got back in december with it :/
The crafted boots are best in slot, and are an upgrade to the your boots (basically a stat+n upgrade). You can probably get the embers from boss kills to make them cheaper.
http://eu.battle.net/wow/en/characte...etzie/advanced is my armory, maybe you want to see how I went about upgrading stuff.
I think my take home message is: Don't let your guild disenchant tank loot just because it has no mastery on it, and don't dismiss an item out of hand because it has no mastery on it. You can buy a 378 belt and cloak for about 400g, gem them, reforge them, enchant them, will cost maybe 800g in total. See how they change your stats, you may be pleasantly surprised.