I have now achieved nine boss kills in Ulduar. I have yet to see any tanking gear drop - note that this does not mean that I've seen it drop and lost the roll, it has not dropped full stop. I have the following kills:
Leviathan (twice - drops one tanking item)
XT-002 (twice - drops no tanking items)
Razorscale (twice - drops one tanking item)
Ignis (twice - drops two tanking items)
Auriaya (once - drops two tanking items)
Since each boss has a ten item loot table, the probability of not seeing any items drop is (9/10)^4*(8/10)^3 = 33.6%. Interestingly, on the raid I couldn't make on Friday night they killed Kologarn who has three tanking items on his loot table. No tanking items dropped then either, which reduces the probability to around 22%.
It's official - the random number generator hates me.
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