IIRC the original purpose behind confusion was to cause the enemy to rethink if it would be worth using the skill or not due to the damage they know they’re going to take by using it. Problem though is that the damage seems to be too little to actually cause that consideration or the enemy simply values the use of their skills to be of much higher worth that the damage they’ll take from using the skill.
My suggestion: instead of confusion causing damage on skill use, have skills gain an increased cooldown based on the number of confusion stacks. This could be a large cooldown increase for the next used skill that consumes all confusion stacks or it could be a small cooldown increase that doesn’t consume the stack. Either way I think this would get confusion back to its intended purpose: making people reconsider whether they really want to use a certain skill at that time, giving the mesmer a slight window of opportunity during that hesitation.
TL;DR: I’m not saying confusion is bad or broken. I just think it would be cool to increase cooldowns instead of causing damage.