There are no addons that cancel pain sup, you can make a /cancelaura button like you do for hand of protection, but why would you? If you got pain sup you surely want to keep it as long as possible, 5% threat reduction is negligible. Nothing overrides pain sup like hand of salvation, which is overwritten by other hand of x's and such. If the tank isn't cancelling it then it must be the priest doing it wrong? In all my years of playing priest i've never encountered or heard of this issue, so it sounds more like someone simply doesn't know the exact details. I wouldn't be surprised if the priest thinks he is suppose to overlap pain sup with the initial impale timer hitting zero, and then a few seconds later when the actual impale hits the pain sup fades and the tank dies.