Kennen needs one additional thing to make his kit complete.

His W should grant a full charge when not in combat for ~10 seconds (or scaling 18 16 14 12 10 8). I didn't do the math to figure out what is ideal, but here is the situation many Kennen players face:

He is too RNG. Riot has done a great job to make his kit feel less RNG than before (the changes to his ultimate really remedied this situation). Giving him the ability to cast W to all those in ult range feels much more reliable, which was his problem before (and the nerfs were slightly real to his solo kill potential, but a welcome trade off)

However, he is still an AP mage. In fact, he is also gated in a very similar way many AP mages are, except he has an exceptional laning phase. His energy costs are pretty well balanced, since he will run out of energy when poking Qs too much in the late game, where as a traditional AP mage would be a little bit stronger (in most cases, and in theory).

Granting a charge on his W will remedy an important situation - his ability to help his team with a gank when needed. Trying to find a minon to auto 4 times, is so unreiable, especially in late game. It feels like a complete RNG situation to have a charge up late game (which can make the difference between a won and lost team fight). Many times, a wave will be cleared, and there is no way to gain a charge. This is pretty whack, and frustrating as a kennen player, when you need to go fight someone bot lane. Look at Orianana, who does a very similar job to kennen. Only her on hit proc is much more reliable.

This is just one of those buffs that "makes sense" and would only help kennens who are actually playing the game right. Either way a kennen will need to help his team mates in a different area of the map. If he has teleport up, then this buff wont even have much effect, since it is fairly easy to gain a charge in top lane. But if the enemy is say diving, or is at dragon, and kennen is somewhere where there aren't creeps around, or doesnt have tp up, then this sucks.

I've been playing kennen since his release (back when people said he sucks hard, even though haunting guise with spell vamp was freepreseason1elo) off and on, and I can't think of a better fix. Let me know what you guys think, or downvote this into oblivion.