Arcane Comet Rework Idea

Damaging an enemy champion with a spell gives you a buff. While the buff is active, damaging an enemy champion with an ability hurls an Arcane Comet at their current location. After not damaging an enemy champion with an ability for 1-2 seconds, the buff expires and Arcane comet goes on cool down. Arcane Comet does reduced damage to minions and does not apply spell effects. Comets will only fire at the first enemy champion to take damage

Why I think this would be beneficial: It would give DOT champions a keystone they can feel good about using. It would make a bigger difference between Aery and Comet. It would make champions who abuse Comet (I'm looking at you Sion) want other keystones.

Other balancing changes: Some champions would become beyond overpowered with this change. So to stop ETC from getting 70% winrates, we'd need to make some of these changes:

Adding a Comet cap. Breaking the cap immediately puts Arcane Comet on cooldown. If I did my math right, a Malzahar ult by itself can spawn 15-20 comets depending on how long you stand in the pool. We really don't need that to exist.

Higher cooldown. The ability to spam comets is a major buff to the rune, so in order to keep melee champions from being gutted by this rune, it would need a much longer CD in the early game. Something like 40-45 seconds at level 1 should help against new comet users going top and ruining the game for top laners.

There's my idea. I'd love a DOT keystone and since Arcane Comet could use some work anyway, why not change it to fill a gap in the current system?