There's really no reason that if she ultimates with just 
that she could very well wipe an entire team out if not immediately focused. 10*level+160% of her AD on EVERY tentacle smacking you (Which can reach up to 700+ damage late game before armor and magic resistance) doesn't make any sense when even 
has consecutive hits from his soldiers deal 25% damage past the first one smacking somebody.
I agree that her tentacles are a bit to strong right now. As I noted in other threads, her tentacles, especially those from her ult, should do decreased damage with each additional hit. That's in line with other champs and still provides a benefit (and feels good) for hitting a large group instead of just using it to beat up one person. Right now, it's like an ori ult. That shouldn't be the case for somebody that naturally tanky. Ori's weakness is that she needs to stay alive to position herself for her ult doing massive damage.
I don't think they're too strong at all considering that Illaoi needs walls to be effective. Fighting and kiting her in open areas can destroy her. If you want to melee fight Illaoi in the middle of the jungle with walls everywhere, you deserve to die.
