At least for a melee. Talking about this from a perspective of 161 - 187 expeditions.

Justicar of the Republic elite mob (and boss) is just annoying. He does almost no damage, but staggers us / immunes himself for 80% of the fight. The fight with him is a very long and very slow running around him just to make 5-6 attacks and being CCed for 2-3 seconds and not being able to damage him for 7-10 seconds straight.

Purifier Veterans knockback melee targets, recover from which takes up to one second. It disorients and frustrates.

Mortalbeasts also do a knockback. Slightly better tho then previous two guys, because it's avoidable (prev 2 are not), but CD on this is around 10 seconds. Have fun killing three of them standing in a triangle. Oh, and this double knockback is awesome. Why wasn't it on the release and appeared only in 1.0.4 or so?

Passified Aurora Knight has the ground sacred damage attack that slowly travels from him to his target and it's hitbox is unrecognisable, but i can say that it is way bigger then the yellow voidzone itself.

And all of this is with Juggernaut Sound Body rune not working. Devs should never take too much of a chatacter control from players' hands.

The other factions are not that much frustraiting. Yeah, cultists have meat golems that also do a knockback, but that's the onle and only mob in whole faction. Yeah, creatures are scattered and you have to kill trillions of them to get to the boss, but that is not that bad also.

Even the Yoldinai (or Yormundurt (or Yogurt, i dont remember what his name is)) flying demon is not so bad, because you can avoid almost all of his mechanics.