If you have never ventured into the <Elitist Jerks> forums, they are a shrine to theorycraft in every way, shape, and form!
Here is some discussion and debate about the current weapon skill forumla, I do not know if this is already included in the blizzard UI or not, next time I respec I can check to see if the talent that gives + wep skill modifies the blizz UI though... http://elitistjerks.com/f31/t11885-rogue_warrior_weapon_skill_adjustment_discussion/
Here is a plethora of information about all kinds of theorycrafting, including glancing blows http://elitistjerks.com/f31/t12855-working_theories_theorycrafting_2_1_a/ According to this the current glancing blows rate is 25% at lvl 70 on a lvl 73 mob... glancing only happens on mobs 3+ lvls higher then you... I am not sure what happens when you are below lvl 70 though.
Hope this helps!