Skilled players already know how to deal with confusion. Its called condition removal or backing off for a couple of secs. Confusion by a Mesmer isnt even the worst kind, because its the ONLY condition they have that is viable. Go up and an Engineer and get trolled with trying to remove 5+ confusion stacks among 5+ different conditions instead.
All in all, the change is for example like doing a blanket nerf of 50% damage on Guardian burning. Unacceptable.