I have many issues with the prince, despite that i love playing him so much. It buts me when im close to killing someone and they just insta-flash out of my ult. then there are the cases where they can just teleport to a minion, dash out of my ult, even sometimes just walk through it.
Fix suggestion #1. Make it impossible to dash or just walk right through it, teleporting will still annoy me but i've learned to work around that.
Fix Suggestion #2, and probably the better one. have his ult mark any enemy champion caught inside. If they leave before the wall collapses the mark will break and cause bonus damage and maybe slow them.
I also have an issue with how pathetic his Golden Aegis is but that's a topic for a different thread.