im not sure i like the addition of a slow to illaois q.
yes, the champion needs buffs. dont get me wrong, i like illaoi as a champion, and i like to play her.
but adding a slow to her q just doesnt seem in the right spirit, or is going to help her a lot. juggernauts are concentrated packages of damage and defense in melee, with little utility in their kits. i feel like illaoi already has a higher than average threat range for a jugg with her q and her e, and her test of spirit is her mechanic to stick to an opponent. not sure adding more utility keeps her identity or will end up making her too strong, which would probably result in damage nerfs.
imo one of the problems illaoi has, is that shes actually not very tanky for a juggernaut. in her ideal scenario when she manages to get between multiple opponents, it feels like she blows up way too fast, and doesnt actually have the time to hammer down her enemies and benefit from the heal before she dies.
have you tried adding a resistance buff to her kit, instead of more utility?
reducing harsh lessons cooldown to 1 second while her ult is active, instead of 2 seconds might be another way to go about it.
the animation times on her w and tentacles are so long, that the actual window between tentacle smashes is more like 3 seconds right now.