Kennen was a good Champion, now Trash
Kennen, was not OP imo but very threatening when her AP damage was still in good shape. Now Kennen is just a piece of crap. If people see you ult now with Kennen, they'll just walk right into your ult and beat the living shit out of you because you have no damage LOL and the FACT you're not even a tank.
The only soul purpose of Kennen ult now, is to stun enemy Champion, so basically Riot just wanted to turn Kennen into a support Champion, that doesn't even have access to Shield or Heal......