I think Illaoi is fair and balanced except for her E.

I can handle the Q. I can handle the W. Her ultimate is strong, but understandable. But her E may be a little much.

I can understand the risk of missing, and to be captured in it, but the after effects a little harsh.

It only costs her 35 mana at level 1 to deal up to 25% damage to my health? If she has 100 AD by that time, it is raised to 33%. Then, at level 5, it costs 75 mana to deal 45%, and if she has 300 AD then it is raised to 69% of my health.

Isn't that enough? No. If she is able to either deal all the damage or you get far enough away, you are slowed and for 60 seconds you must not only play the game but also avoid her passive that can deal 10 (+120% AD) at the least. I can either dodge 6 of those things or try and destroy 3 to stop it. Not that within 20 seconds, Illaoi is able to use it again.

I don't want to change her passive. I don't want to hurt her in any way. But that time could 40 seconds (still sending out a tentacle ever 10 seconds) and it would still have the same effect.

Its also unfair with no counter. If I get caught by her E, I could either get dealt a huge amount of damage and then avoid the tentacles, or get out quickly taking some or most of the damage and also avoid tentacles.

Why not just say "if you kill two of them, you are freed." and allow us to play the game. She already has strong abilities. Her Q deals bonus damage and can heal her if it hits a champion. Her W gives her a dash and bonus damage. They aren't even that abusive until you play her enough. Her E as of right now is very abusive and I fear its future.