Okay, so I have both Nightblade and Iceburst Brandish.

So one time when I was doing a gate, this time I had Nightblade, It does Normal and Shadow damage. So i went up against a Gemlin, and instead of doing the big yellow star it just did the normal (blue) light.

Then Another, time when i was doing another gate, this time i had Iceburst Brandish, and i went up against a lumber. Since Iceburst Brandish does elemental and normal damage. It should have been super effective. But it did the same thing as the nightblade, it showed the normal (blue) hit instead of the yellow star.
Then when i was poisoned, thats when i did a crit (yellow star) against the lumbers.