A couple things that need counterplay in order to balance

1. Knock-ups and displacements still need counterplay of some kind. Being able to essentially stack these kinds of CC in order to keep teams reliably locked down with no way to retaliate remains an issue.

2. While Riot mentioned that healing tends to take away the fun of games as it removes what players have done, shields remain largely untouched. While undoing damage is unfortunate, there still remains counterplay to that (grievous wounds). However, shields have absolutely no counterplay while essentially mitigating the actions of players. Arguably, you hit champs between shielding, but this isn't a viable tactic when caught in a drawn-out fight, meaning teams that stack shields can actually be far more useful than teams that heal as a shield will always block as much damage as it can rather than being affected by any kind of reduction. While these are temporary boosts to health, again, once teamfights are occurring, they are far more effective.

These are just general game mechanics. In terms of specific champion issues, safety still remains a dominating factor in the game which is shoving out a lot of champions from being prime or balanced picks.