Actually it's a big gameplay change. I don't know if you can see if someone gets damaged by one, but if you get knowledge of where the enemies are, then that's basically free vision, and a pretty good one.
EDIT: I read the ability, and right now, it grants vision in a small radius around him and also grants vision of the targets that were damaged by it. Again, though, having essentially a notification would change the gameplay. It's kinda the same as asking to have a ping on your map whenever you spot a champion on a ward, which would increase map awareness drastically. A lot of time, people don't always watch the minimap, so they miss people walking over wards. This change would essentially make it so that they have the system watch the minimap for them, which is unfair.