With few exceptions i really wonder what you think. Will be viable in higher levels of play because the only reason i think you would pick him now because he is lane bully and does damage (but why don't you pick Irelia). Thanks if you if you answer and also to any Garen player.
It really depends what 'higher levels of play' means to you.
He will still have some strong lane matchups due to how overbearing he can be for certain melees, albeit fewer good matchups than before most likely. However, he'll also be more valuable in matchups against tanks like Maokai or Shen. Whereas before, you could pick these tanks, stack some armor in lane, and count on Garen being useless later on, but that should be less true now. Since we're moving him toward more of a carry, Garen doesn't lose when he goes even anymore.
I can't say whether he'll be an LCS pick or not, since they tend to value very particular character profiles and don't often pick pure melees as often, but hopefully he can be a strong pick in Masters solo queue. Internally, I've got Masters and Challenger players telling me he feels really strong now, but I guess we'll have to wait and see!
My guess is that they will find they need the villain to be the priority target, and the fact that they can't control who the villain is means it will at least occasionally be on a low priority enemy. Because of this they will pick a champion whose damage is more targetable so they can focus who they need to.
Of course I'm no challenger player so I'm just spit-balling here.
