What RIOT needs to understand about balance.

Mobility itself doesn't create an unbalanced game.

The vast majority of the issues in the game in regard to balance come down to two things.

1. A champion can quickly go in to exchange damage without putting themselves at risk. Examples: Nidalee, Zed, Fizz, Kalista, Leblanc, Lee sin, Ahri (at various stages), Pre nerf Kassadin,

Take a look a Ahri as an example for this. Riot reduces her damage and gives her an increase to mobility from Q. As a result her winrate goes from roughly 51 percent to nearly 60 percent over night. A champion that is able to get in and deal damage is not actually at risk if they can just as easy get back out. The recent nerfs to Kassadin also show how important this concept is. Kassadin can now get in quickly but do to ramping mana costs and range reduction can no longer get back out. Combine this with the damage nerfs he has taken over time and as result he has been made nearly useless.

2.* A champion can quicly go in and reliably (such as on click) do so much single or multi target damage that there is little the opponent can do to react.* Release Xin zhao, Riven, Gnar, Lissandra, VI, Jarvan, pre Nerf Fiora, Pre nerf Akali, Katarina, Pre nerf Warwick

Warwick at the beginning of season 5 was a clear example of this. Use R to gapclose and explode the enemy champ before they can do anything to even react. You now are left with a 5vs4 and with the only penalty being that Warwick is lacking an ultimate for the fight to come. Early Xin zhao and katarina are also clear examples of this in that they get in and delete someone before they can even think to fight back. 0 Counter play.

Note that some of the worst Offenders are actually guilty of both of these issues and as a result become some of the high win rate/most toxic champions the game knows.

The solution is to look to healthy champions such as the current state of Diana or Aatrox. Both can get in and do significant damage however they must stay in and put themselves at real risk.

On the other hand If a champion is able to get in and out easily they must have their damage reduced significantly to compensate. An example of this would be Ezreal who is able to get in and out of combat fairly easily but must land successive skill shots to do significant damage to someone.