^im not clear on your maths, but I will say this 7.69% parry chance is probably close to the amount of variation in actual attacks parried you will experience on any given encounter.
Ive ranged from 20% parried attacks to 38% on the same fight with the same gear.
So my point is that, you would be correct if that 7.69% parry rate was guaranteed but it just isn't. It's RNG.
Over a 1000 fights will you get more parry than me yes.
But in the short term, we could have the exact same stats, and your parry rating could be 100 higher than mine, and there would be fights where I out parry you.
This is why I am personally against parry rating. It's nice to have, but stacking it is pointless.