I feel the "inconsistent damage" you showcased in the third video is actually the game working as intended.
The first hit was the lowest damage one because you hit him at a very early part of your swing. I don't know your character's level and one handed skill level, but based on armor stats in single player, the AI is wearing one of the best armor sets in the game and his arm armor certainly passed 25, thus you did 1 damage.
The second hit was on the head, since there's a bonus versus head and you hit him at a much better part of your swing, you did 64 damage total; and again since he is wearing one of the best helmet, 45 absorption is not unreasonable.
Third hit was also on the head but you again hit him on a much earlier part of the swing than your second hit, despite with slightly higher speed, you did 50 damage total, almost same amount of armor absorption.
The fourth hit was on the shoulder, you did 41 damage without headshot bonus, and it was also far from a ideal hit because you can see you hit him near center of your blade (I can't recall exactly but the sword in the empire tournaments is a pretty long one, I might be wrong here), and if you notice the location of the crosshair when you hit him, the hit occurred at a later part of the swing, again, not ideal. As the absorption amount, as we could safely assume the shoulder armor is much better than the head armor, (you can check the pieces on the market in single-player) 39 is not unreasonable given the previous example.
I will not go further as it is the same logic, the same rule. Another factor is that you have a much taller character, your left swing will be more likely to hit opponent's shoulder plate, which is the most armored area; besides if you don't look down a little bit when doing a overhead swing, it will also hit a bit later than ideal.
Besides all these, you are hitting the most well armored character in the game's current setting with a one handed sword, which does CUT damage in swinging. The armor would be less effective literally in EVERY OTHER scenarios.
Now, should armor block this much damage? Perhaps, perhaps not. Should we be able to reliably quickly kill a character armored to the teeth with short swords cutting? Should the dev lower the damage threshold for animation interruption? Answers to many of these questions are subjective. Should we be able to choose our weapon in tournament, so I could bring a mace to that fight? I certainly hope so. But, to say that the damage dealt is "inconsistent", which implies a mistake on the games part is not true.