With the spell active and in the dark it no longer gives away your position when you're hidden, that part is fixed but now the attack bonuses for myself and my enemies in darkness don't seem right:
I brought out my old fighter character for a test. Here is a screenie without Cat's Eyes:

Notice the spell is not active. Everything seems in order. Both my character and the opponent get a -20% chance to hit as it should be in darkness.
Now here is a screenie with Cat's Eyes active:

First off my character is still getting the -20% chance to hit. Is it supposed to be this way? If so then what's the point of Cat's Eyes? More importantly my opponent is suffering a WHOPPING -50% chance to hit!!! I guess I shouldn't be complaining but this doesn't make sense and frankly would make the game too easy for me.