I dare to say i have some good ideas to fix illaoi
i played A FEW normals with her (yea a few only) and i can say what feels really shit
passive: just let us point and click to where we want the tentacles. they dont give vision i like that but we cant use them to zone they spawn random. and they always spawn in the same place. if i want to stack 10 on top i should be able to do that. also make them like azir soldiers. if i right click an enemy they attack if they are in range. give them a cooldown of 5 sec (for the autoattacks so they dont attack 24/7) UNLESS someone is my vessel or i used my ult. if thats the case they should always attack if anyone is in range. without stop.
q i think this one is ok
w feels also ok... but either higher base dmg or higher ad scale
e make it so it ignores minions and maybe give it a feature that nidalee got aswell (and made her a s tier jungler. allow her to grab the souls of jungle creeps)
r buff the range to amumu ult, right now the range is so small its a wonder when you hit anyone. it doesnt even fill the whole baron pit. as soon as illaoi hits 3-4 ppl every runs away because the tentacles + black cleaver destroy a team and heal her really well. but the problem is... even on aram with snowball you barely hit 3.4 ppl!
so yea those are my ideas. she was a new champ and you just doomed her please dont let her die.