We have had multiple reports of team members failing to debuff the counterattack skill with debuffers. So far it has happened to me with Sabina and several others with Sonyia.
So either this isn’t riposte and can’t be debuffed or may be a bug. It would be harsh if it was the prior.
In my case yes: after one of my alliance members pointed out it could be due to Wu I checked that anytime the dispell did not work the text “missed” appeared next to the titan