Forget mobility creep...
Who is ready for Anti-mobility creep
Azir, Viegar, Poppy. sure, it is not wide spread yet but if more and more champs keep getting anti mobility abilities a dash will become a major weak point of a champ's kit especially if they are extremely reliant on it.
Riot do not make the same mistake you made with mobility by adding far to much anti-mobility to the game. Some is understandable but if it starts appearing on every other champ you will just replace one major problem with another and in turn be back to square one where only ranged champions are being played.