Ok, so your argument for rupture is that someone wouldn't figure out why they are taking damage. How is this any different than undying rage, a new player would be wondering why tryndamere isn't dying. It just says ENDLESS RAGE. No new player will understand why they can't kill him and he is killing them. Why not implement rupture, and have the words DAMAGE WHILE MOVING flash above his head? That's basically what endless rage is, except would actually tell you what it's doing. Or like you said, in the death recap, put a description of how rupture hurt them. When I first started, I didn't understand why some of annie's casts stunned me, I didn't know why I got slowed after twitch hit me a few times, I didn't know why mf's double up hit me seemingly where ever I went. The "don't understand" argument could be applied to so many current skills.
Dunno, maybe it is just as simple as I disagree that a new player would take more than 2 or 3 tries to realize that rupture deals damage based on movement.