Your thinking about her is understandable, but Personally I think this restriction was introduced for “balancing purpose”.
In fact, the fighter that can stun enemy over 6 seconds other than her is only Fire Branded with over 3 enrage (too hard!). Her bang bang bang is 3-hit, Which means she can inflict stun up to 25% ×3 easily and has a chance to reset CT by her marquee (My stats of Dream Catcher is bang bang bang×4 & BB3) , It's a little too much from general point of view. If there wasn't a restriction that it can't be activated on dark, she would definitely be OP
In my opinion, She “used to be” really powerful, but recently strong dark fighters like Death Wish or Unholy are increasing, Her opportunities to shine are decreasing little by little. Of course, she is still strong enough against team with no dark fighters.
