This proves nothing because there are lot of possibilities that cant be properly accounted for with the naked eye.
First of all, using an assassin as an example is bad because they have timed blocks. Even if they are blocking for the first 9/10ths of the attack animation, if their block was slightly premature and it expires during the last 10 milliseconds before the attack connects, it will not (and should not) count as a block even if it appears as though it should have been blocked.
Furthermore, even if a non-assassin has their block up for 9/10ths of the attack animation, if they give the game an input that makes them stop blocking at the last moment, it will look like the block failed when the reality is that they stopped blocking. If you slightly mistime a parry, dodge, deflect, hidden stance, full block, or just do something stupid like accidentally throw a light attack, you make yourself vulnerable the instant before the attack lands but the game doesnt have enough time between input and hitstun to show you a corresponding animation as proof of user error.
The fact that OPs examples all consist of slow heavy attacks penetrating assassin guards makes it HIGHLY likely that the assassins are just blocking prematurely and arent experienced enough to know they need to recenter their analog and refresh their block to keep it from expiring.
If this were a real issue with the game, a LOT more people would be complaining about it. Not saying this definitely isnt real, but this thread doesnt make a convincing argument.
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