Please hotfix Kennen!

There is little to no escape from him because of the large radius and with how fast the bolts come crashing down. It's basically an Amumu Ultimate Sized Annie Ultimate that moves at 600 movement speed that applies a Rylais Slows.

Combo his inevitable teamwide stun with 788 (+1.5 ability power) from his ultimate and then another additional 235 (+75% AP) and you end up having Kennen running into a team fight and destroying the entire team by himself, no one should have that much of a large AOE burst with that much lockdown, not even Annie has anything remotely near that burst and Veigar requires to land his E and be super farmed in AP.

TL;DR: 1k base damage + 2.25AP ratio aoe burst that stuns is not a healthy mechanic.