In general, there (in the game and on the forum too) the information about "To Hit Chance" is not presented.
There's only Attack Power measure and some info about it here and there. While, it's obvious, it's a different things and a different questions, "What the Hit Do?" and "How the Chance to do a Hit?"
Yes, Parry is a relatively weak style in the sense of ToHitChance.
And yes, it's possible, in my opinion, the Surprise Ending skill defines only WhatHitDo-component.
Though for me it's not so interesting: Since we almost hasn't instrument to control when and how this skill works, it's just a rare-working blocking skill for me, with funny results -- sometimes...
// Also, counter and pure-offensive Theatrics rely on their Hits. So, these guys needs a little attention on their Chi stat. And Chi is related to the discussed skill...