I watched the entire video at 0.5x speed because I love you (in just the same way Christ loves all of God's children), and I have to tell you that while there is some bullshit on display (Freja's laser, Stone Dragon's stomp, Mimic's bite are all notorious), so so many of these are just bad animations due to roll hyperarmor. Hence all the shots of the player
seeming to get hit right after rolling by an attack hitting the air behind them. You've never seen the player get staggered directly out of a roll in Dark Souls 2, because FromSoft made the strange decision to make that impossible.
Every single Sir Alonne grab clip (in fact, most of the grab clips in the video, I won't defend the Mimic hitbox but most of the rest are fair) sees the player panic rolling at least a half second early, getting hit during the latter portion of the roll, a late stagger animation playing, followed by the "teleport" into the grab. Grabbed while they were way over there!!! So unfair!!!!!1 No, not really. If you wanted to argue that grabs should only count for hits to center mass and "glancing" hits should just do some damage, I would largely agree, but a bad grab rule + bad grab animation =/= bad hitbox. Moreover, it's still your fault if you panic roll
towards a guy's sword when he's charging up for a stab.
You can find plenty of equally egregious examples in Dark Souls 3 (including grab teleports), take
this "bad hitbox" compilation starting at 37:00. It's just a reality with all of these games. Dark Souls 2's issues are exaggerated due to the Agility system and some really poor choices about how to handle the visuals, but it's not drastically different.