I noticed that sometimes some enemies are very frustrating to deal with. This situation happens on normal side swings and rarely for thrusting. Two scenarios usually happen that I call them "height hell":
1- Your character's relative height to the enemy is in a way that almost all side attacks gets blocked by the end of the enemy's weapon near the handle. The enemy can block you with minimal effort by just facing toward you.
2- Your character is way taller than the enemy and your side attacks pass over enemy's head and enemy can land a free shot on you.
Usually in both scenarios the enemy has advantage because enemy's side attacks barely gets blocked by your character. The situation is worse in scenario 1. In scenario 1, your character is usually miserable to defend.

This image shows scenario 1 case:



Based on my experience with the game, the AI doesn't have too much variety and this frustration is not due to any randomness in the AI behavior. This is just because your height compared to the enemy's height puts you in a disadvantage. I didn't investigate all heights to see what should the enemy's height be so that "height hell" can happen but it seems like this happens when the enemy is slightly shorter than you. Maybe people who have some fancy tools to experiment can investigate my theory either approve it or disapprove it.

First we need to focus that being tall has the advantage of moving faster. Since the best defense is to walk back instead of trying to block enemy attacks, being tall is generally favorable (except in very tight corridors that moving is not possible).

The first solution to this problem is to avoid max height characters because in this case there is a high chance that a short enemy harasses you a lot (specially enemy with shield). The best solution I found is to go for around 70% height. In this case, you are almost safe if just passively move backwards but some taller enemies can catch up so you should attack while retreating from time to time to just keep enemy at bay. If you miss a swing passing above the enemy's head, the enemy almost always does a cheap shot on you. Try to be more conservative in this case.

The weakness of the AI is that it performs very slow and stupid overhead attacks that never has any randomness on where it aims for. This means that if you turn around the enemy you can always dodge that. In this case, your patience is tested to perform walk-back constantly and wait for this type of attack. It will be boring but it'll be safe. You need to hope that some of your shots are not blocked by the enemy's "height hell".

Crouching can be dangerous for two reasons, first, you get slowed down to back up, second, you may fall on the ground. This solution is useful if your patience is running out.

The last solution is to perform fancy attacks such as overhead-side attacks. This type of attack is special because it is harder for the enemy to block it. There are more fancier types of attacks that legendary players perform but I'm not qualified enough to discuss them here.

***Side note: The AI never actively tries to corner you. This means that the enemy always oscillates between moving left and right. For instance, you may feel that an enemy is cornering you by moving a bit to your left to perform a swing, but the AI always moves to the right on the second attack. This means that to avoid getting cornered in the conservative walk-back approach, just take a single path, don't change it because of the enemy moves, just wait for a second, then continue. The enemy always does one left walk and one right walk unless it is blocked by something very close to it.

Finally, I wanted to mention this interesting phenomenon that bugged me out for sometime thinking to myself, "why do I lose to some arena fights while I'm not a bad player?". It should be noted that "height hell" can happen to the enemies too. This means that almost all enemy attacks get blocked by you and almost all your attacks passes the enemy's parry. "height hell" is not a binary situation, it can be a mild situation or a serious case that puts you on edge.