Why do three-hit passives on Ekko and Jax apply spell vamp but on-hits like Teemo's E don't.
Every three hits at level 18 Ekko deals 231 (+70% AP) magic damage and Jax deals 220 (+70% AP). Both apply spell vamp fully.
Every three hits Teemo deals 150 (+90% AP magic damage) and Kassadin deals 60 (+30% AP). Neither applies spell vamp.
So the "every three hits" thing definitely has the advantage.
It would be nice for people like Teemo and Kassadin to have some sustain in the field when people like Jax and Ekko can just get spell vamp and never recall.
There are a few three-hits champs (Diana and Gnar) who don't apply spell affects with their abilities and it would be nice if they did. Like Ekko gets a massive movement speed steal AND it applies spell effects, and Diana's is just AOE (spell vamp is 1/3 with AOE remember.)
For anyone who is wondering, for me personally this is just to make magic damage on-hit Thresh viable.