The 3 rounds knockdown seems to be a rule, happened against Enchanted Armors in the Withered Gardens.
Also noticed that "Winged Feet" of scoundrel only affects the caster, I had a fight lv4-5 against enraged undead boars and undead near Cyseal. An undead caster affected all allies in his area.
Seems to me skills are upgraded for the monsters when it's possible.
I am surprised I am the first to pick this out.