I have rewatched your video several times (some of that at 0.25 speed) and have not seen anything that would indicate a stun from an enemy player.
That being said coupled with lag most CC abilities in the game can fail to display their animation on the target (the one i notice the most being petrify), but those are usually coupled with at least a partial disply of the effect (uppercuts particle animation for example still plays, even though you don see your charackter getting knocked up).
Your character here seems to be perfectly fine, if not for your comment that you were unable to do anything. Additionally your character manages to "dodge" an attack, while you are stunned, and i can not see any source of the evasion buff on you. Similary you did not perform any dodge roll as this occured (your last action was ambush). So i assume your character was in fact stuck in some sort of lag, and while the dodgroll itself (which i presume you tried to perform there) did not go off, it still managed to evade an attack.
Thus I would fault server lag here.



Also something i noticed way too often both in game and on the forums is accusing others of macroing/hacks/exloits and similar, without any real evidenc but "i got pwned he must cheat". Take care and ask others for advice, just like the OP did. He even gave a video as example .

However if you indeed notice this very special behavior (note the lack of animations AND particle effects here) multiple times facing the same opponents something starts smelling fishy, especially if others experience the same.
I am no expert on macros (only ever used the tool in wow) and have no clue how the ever so famous "lag-switch" actually works, but this doesnt seem like something i would expect out of those either.
Also keep in mind that the "always with the same players" part can also be attributed that these players choose the same campaign as you did. They might play most of their time on it, just like you, so you are bound to stumble into each other more often. And if your campaign is something like thornblaed i wouldnt be surprised if they suffer from the very smae lag you do.

After further investigation, I am not sure it has anything to do with players using macros. This video is immediately after login, after sitting AFK for a few minutes.

-Skills are locked
-Cannot swap bars
-Cannot roll dodge
-I am not sprinting (not physically)
-I am not stealthed
-I am losing stamina while walking
-As soon as I hit low stamina, the bar unlocks.

I could speculate that I logged off previously while stealthed, thus encountering this strange error mode on the next login. It could be that I am "stuck" sprinting as I do seem to be moving faster than a run. This seems oddly strange to the previous video I had posted. However, it may be an entirely different situation and have nothing to do with it.

https://www.youtube.com/watch?v=Ibl5fFYHVdw&feature=youtu.be