Bug or not - Assassin's Spell Negation

[BB Shockwave]

I faced LOTS of Assassins in my second game in Orcs on the Marchs, and - let me tell you - they need to be taken out of the field quickly if you are playing for no-loss. So I tried various ways, and - not that I am compaining - oddly some worked, although they shouldn't...

-Faun's Fatigue ability can put the Assassin to sleep for 2 turns, just as it says. What's more, if you use Nightmare afterwards, they will have Fear cast on them. Shouldn't that disappear?

-I did not get the regular Magic Lock spell yet to try whether this works with the spell too, but the Witch Hunter's Magic Lock works fine on Assassins and does not dissipate...