I didnt find this on forums so...
If you use 'rupture tendons' skill on the enemy without armor so it would proc, then save & load the game, on enemy turn it wont take damage anymore.
Probably other effects are subjected to this as well.
Me reproducing this bug on video (spoilers from Act 3/Nameless isle):
https://youtu.be/JCbKLQmpM5MLarian please fix
