What is wrong with your argument is that you are using it for ranged but not melee
Because melee has no random factor. As said, you only get hit if you make a mistake. Getting hit by ranged depends more on what the archer does and the random chance created by flight time and large crosshair.
As for your math, it's correct in theory, but your probabilities are way off. Going with 95%, there's only a 57% chance of blocking ten hits in a row. The thing here is that is
varies greatly from player to player because it depends on your skill, and again, you have to make a mistake to get hit. For some it's a great deal less than 57%, for some a great deal higher than 57%. And that's what makes it okay, because it's based on
player skill (of both players), not chance. You are saying there is no difference between this and there being a 20% chance of getting hit per shot from X distance, no matter what you do, based on pure chance. This percentage also varies, but there is only so much you can do to decrease it: there'll still be a relatively large random chance of getting hit from a moderate distance because of how the game mechanics work.