I think this would still cause visual issues. If you hovered over a minion to see the health bar, what would happen if you hover over an entire wave thus seeing all the health bars at once? Or what if you're trying to target an enemy champ, but the health bar is obscuring your cursor since the enemy is behind/inside of the minion wave.
It's a great idea to make health bars more visible, but I think this is an issue with the UI and how far spaced everything is rather than an in-game visual display issue. If they changed the UI to where your champ information/health/and whatever you're targeting is right above your spell bar, I think that would make things much easier since you're already looking in that general area.
Blizzard made this change with WoW since they realized no one looks in the top-left corner when they play. People mostly modded their UIs to have their information in the center/bottom center of their screen, so Blizzard made it easier and put your health bar/mana bar near where your character is on the screen so you can see it better during the midst of fighting.
Riot might need to make a change similar to that with minion health and other things. Or at least what you're targeting appears above your spell bar. They slowly started doing that change (allies above the minimap), but as always they could do better :)
