He doesn't really need nerfed...though it's true that he can still Medatank to a point. I mean they even had him tank 3 people and dragon in the video they did for the patch. Though he didn't heal back to full so the change was obvious.
I've notice something though...people on the forums complain about every champ that has any kind of reset and is calling them OP. Yi and Kat seem to be the main one, both are squshy and countered heavily by CC. Kat has been built tanky lately but yeah, I already gave my thoughts about that on a different thread.
While the reset function might be frustrating, the facts are that you can stop that with CC. Not only that, but to get the reset they have to clean up pretty much. I don't think either Kat or Yi do as much in a team fight as other mids do. You have to already be losing the team fight for them to clean up. Even if you won the team fight, your team would have to be low health for them to get the reset. And from what I've seen, most games where the mid is Yi or Kat then those team fights end up being a 4v5 with them coming in when the fight is done.
Yes they can reset, yes this means that can get multiple kills. But there are down sides to even having them on the team. If it's really that much of a problem then buy a GA. No kill means no reset.
My biggest problem with him is not the champion but the players exploiting his design. Meditate was designed for sustain not for tank. It really shouldn't scale with anything tbh, and is probably best to be reworked into something else but i feel reworking it is wrong because his kit makes him unique. Just make it so you can't meditank, like add something that if being attacked the heal amount is reduced by X% and make turrets interrupt his heal.