Okay. Small sample, but a sample none the less.
Me and Holy Paladin. First went to Kara. Get to Attumen.
Results:
Meph - 2 taunts. - Immune
... wounded.
Anyways. We next tried the Raptor boss in ZG. Killed the Raptor so not to screw the results.
Meph has
Enlightened Judgements. Thus giving him 4% hit rating. I had Righteous Defence Glyph and no hit rating gear.
Diocaska Taunts - 139 / Sucessful taunts - 131 / Missed taunts - 8
Mephasus Taunts - 132 / Successful taunts - 118 / Missed taunts - 14
Diocaska missed taunts = ~5.8%
Mephasus missed taunts = ~10.6%
Again, in such a small sample, the data is most likely unreliable, but what can be concluded from the data is that it appears to be a fair margin over being 8% or 9%. Under 17% by over a 1% margin, but in such a small scale, its very likely to happen.
As Meph has a base 4% more chance to miss than me (Enlightened vs Glyph), the results don't seem too far away.
Willing to believe that its very likely that it works off the hit table. Its also very likely that most bosses that have taunt as a required mechanic have it set to melee level (8%). (I still haven't found a combat log in Naxx where I've missed a boss with a taunt with low hit).
I'd like to request someone upload the log somewhere else, but here is the tempory link.
http://w19.easy-share.com/1903262909.html_________________
"Good tankadins know all the fundamental rules of tanking
Great tankadins know when to break these rules" -Passionario