Just played against a SUPPORT Illoai. She went 9/1/6...
I don't think she broken per se, but I think a few things could be done.
Change tentacle spawn times; perhaps they spawn less often &/or start at a later level.
Make her tentacles unable to spawn on enemy towers or make it so the tower will target them.
Tune down her base dmg; self-explanatory.
Make her spirit ability break when you get too far away, but shorten the range.
I really like her concept, but it's a lot of tentacles to play around, especially in the early game; imagine teemo having 5 mushrooms before lvl 6...