Just my opinion, but Kennen might need some nerfs in 8.4

With Spellbound orb, Liandry's buffs, Morello no longer giving mana and giving magic pen and health instead, as well as Twin Shadows returning, and Rabadon's being buffed, it might make Kennen really strong. Spellbound orb and Twin shadows make it easy to stick on multiple people, and Morello and Liandry's can give you a lot of health as well as Magic Pen. My suggestion is that you further decrease the damage Kennen's ult does per bolt, and his E movement speed. Since Spellbound orb seems like it would be an almost essential item, it will make it a bit more difficult to stick on people if his E movement speed is decreased. Also, since Kennen already loves Liandry's for the burn, magic pen, and health, the buffs will make your ult a lot better in teamfights. Kennen already had a pretty hard time dealing with tanks, so the Liandry's buffs will help.

Tl;dr, because of the ap item changes and additions, Kennen needs to be nerfed.