Kennen's passive is the problem.

It's a ticking time bomb with no real counter play. And almost always guaranteed win trade for Kennen if he gets that proc in laning phase. It's annoying to play against when you know he's gonna get that stun off most of the time or zone you out from minion wave. Sure I could play safely and freeze my lane near turret, but sadly it's not that great of an option because he's ranged and I need to watch out for his poke. Kennen is a "team fight" rat, then focus on that. Rework his passive to something which would benefit everyone in team fights or himself.

EDIT: I'm okay when he gets stuns all around team fights, but in LANING PHASE (you were meant to do that bro, go ahead! :))? There's no way to properly counter that unless you're getting your junglers aid. Or play like a chicken. Kennen has no real identity. We all see him as team fighting god etc, but we forget about how obnoxious it is to lane against him. There needs to be some sort of a middle ground around his kit, mostly involving his passive (and W passive from auto attacks).