The functional miss chance is rather less than you might think. Miss chance has pretty steep diminishing returns as the cap is only 16%. The 5% base is also reduced by 0.6% if you're being attacked by a raid boss (level difference). 6% is a bit conservative though, it is true, especially when you add the 3% miss buff from Hunters/Moonkin.
I wanted to be conservative though to show the best case you could expect from SoB. =)
I think, in full raid buffs, including the Scorpid Sting/Insect Swarm, I'm sitting at roughly 11% miss, on my DK tank as Blood.

