Two worries: 1 is pushing champions taking this and poking the enemy to get the burst and using that to push in the wave, especially with a 35 second CD. That could be fixed by making it champion only though.
The second one is that it prompts you to not want to poke your opponent because you lose out on all in potential. Electrocute for example requires 3 damage instances, meaning that you can poke without losing your burst. Meteor on the other hand comes up more the more you do poke, and is meant as a poke one in the first place.
I also just generally feel like it is a more niche version of Electrocute. The champions you mentioned generally want to take out a single target as quickly as possible, Akali for her R reset, Diana because she is focused on trying to burst someone down in a very short amount of time. None of them have much use for doing damage in a large AOE at the cost of single target burst, and post laning phase if their kill time takes 3 seconds then they are already going to be dead anyways or their damage is so low that this keystone wont make up for their lack of burst.
What I do see happening is J4 and other similar divers focused on AOE taking this, although most of them can just take aftershock for less damage in a smaller area, but with the resistances to actually live long enough to kill their opponents. Of the people you listed I could see Elise taking it purely because her mid-late game teamfight is a bit weak and it helps her provide some more damage for the team, and even then she would only be able to take it because spider form E lets her survive that long in a fight.
Yes.
with this.
W hitting an enemy count as a spell?
