While I get the frustration, the way to deal with them is to prevent them to do that.
It doesn't always work, but knockback, knockdown, holds, etc... when they are near to activation prevents them and while they are otherwise prevented, that's when you hit them with a larger attack defeating them.
If they do manage to get it off, then you deal with other stuff in the case of Fake Nemesis, but MoG is just a bit harder to hit.