I'm not mad that Ahri has a new skin, but why a legendary one?
https://www.youtube.com/watch?v=ZCt97vpQs_I
I'm not saying that there isn't a precedent for a champion having more than one legendary, and if Riot sees a chance for one, then go for it, but she already has Popstar.
Soraka has skins, but never a legendary, and she has one of the fewest lines in the game.
MF has skins, but not a legendary, and people have been asking for a VO update for months. This could've been a great opportunity for one, or at least the skin.
Syndra never had a legendary, and her better skins are legacy. A light-hearted VO would have been great.
I wouldn't even be mad if Ezreal got one. I don't think having an Ultimate should lock you out of legendaries, and having him be cocky as he lanes against Jinx would've been hilarious.
EDIT: Turns out Popstar isn't a legendary. Still I have to ask why her rather than the others.