Illaoi's E's scaling is a little strong atm

It just deals too much damage for how safe it is. It's long range so you don't put yourself in danger, it moves fast enough and retracts fast enough so the enemy spends most of the animation dodging the skill and has no time to punish, and at rank 1 it deals up to 32% of the targets hp uncontested (if you approach then you you might also take damage from her q/passive tentas which hurt more than the soul itself.) The problem lies with the kit she was given. If she has any tentacles available then you can't fight her. Her e prevents you from extending to kill said tentacles. And her q punishes you for positioning behind minions (even if you dodge it she's pushing the wave and you have to spend even more time dodging stuff. And on the topic of her ultimate, I know people like to say "just walk out of it" but then forget that she's just going to stick onto you with w. Even if you could just walk away it's still the concept that her kit is just "don't fight her."

If the best advice you have against a champion is "dodge their skillshots, run away when she ults and hope she doesn't kill you anyways" then there's probably a problem with the design.