Yes, 25 at a time is still quite tedious when I have thousands. Especially since there is no checkbox to select all those 25 at once, so I have to click 25 boxes.
I am not sure how well received it would be from my members to have all their notifications deleted though.
I had also contacted the author for AIO plugin and they found it was actually a bug in their previous update (which was August 2nd). The issue was reported by several users and they were able to reproduce it. They have already fixed it with a newer update.