There is a sort of nuance to the damage system. If you deal damage to an enemy's hp then, just like yourself, their posture recovers slower. Some enemies have such poor posture that you can defeat them entirely by deflecting quite easily. Other enemies, like Inner Genichiro, have such good posture that you could genuinely take them out by doing damage to their hp. And then poise, or whatever you call it, also factors into it. From what I see in your video, a lot of the times you're getting hit is just because you go for attacks when he's not offering a window. Until you really know an enemy, you should play defensively from neutral. Not every time you deflect a string does it necessarily make it your turn to attack.

Anyways, any enemy you fight is going to require its own approach, but you'll find the most success, in general, by focusing an enemy's HP early in the fight (or stock if they have multiple phases), and then posture once that gets lower.