Soft Spot for Mobility
No one likes playing against the Leblancs, Zeds, and Katarinas etc. just admit it. Whenever you die against these champions you don't think "He really out played me there, I will improve next time so it won't happen again" it will be more like on the fly reaction of the champion killing you and you going "F[][][]ing Bull S[][][]!!!". On the flip side if you get out played by the Xerath, Vel'Koz, or Syndra etc. you will pretty much go "That was a good kill he got, he played better" or "I messed up, I deserved to die there, I will know what to do / not to do next time!".
But a champion coming from two screens away to one shot you out of no where vs a champion that requires skill and cannot simply come out of no where to kill you; and also probably cannot simply one shot you and needs a little more beyond their full combo to fully kill someone, also actually has the pressure of actually usually skill to get their kills and to avoid getting killed.
tl;dr : Riot has most of their immobile mages verily balanced for the most part; while on the flip side their assassins are typically insanely overpowered and remain in that area. I want to say Riot has a super soft spot towards assassins and refuses to touch them at all (Nidalee is here too by the way, Riot's beloved kitty that they will never harm) because apparently League of Legends is a spectator only game and requires 'flashy plays' forgetting that playing against a bunch of mobility champions is not fun at all. Sure blinking every where as Katarina, Kassadin, Ezreal is fun and all and jumping mindlessly as Nidalee; but the people who have to play against this are not having fun and you see mobile champions the ones being banned. Unless you are Froggen you don't see the Anivia bans.
