Illaoi needs buffs. No, she's not OP
She's down there with Cass, Kog, Morde... heck, her lose ratio is more than Yorick's and even Urgot top has more victories than her.
She's a strong lane bully, but her whole kit has ways to be avoided, and it's too dependand on tentacles that take too much time to spawn and even tho they deal quite the damage every punch, are very easy to telegraph and avoid. In fact, some strong tops such as Nasus and Garen would THANK Illaoi for her kit, as they're getting more stacks with only a couple hits, not to mention ranged tops get free gold.
Her ultimate can make or break, but then again, it's a matter of just stepping out of it, and it's done, you just can deny all the ult's damage by NOT FOCUSING HER, THE TANK... and that's what most people does ayways.
Her E is scary on lane, and only during the early game. During team fights, you're better off focusing the opponents than ripping their souls appart, since the damage you do on the soul is still VERY low and it's only useful for getting opponents who are running away... if it hits, because the casting time is slow. I mean, after 12 minutes you can use the E on most AD based tops and they can just wait for you to end up mauling the soul or just go and have at you because well... it stops being scary.
She can do some interesting stuff, like, pulling the soul out of the enemy and letting the turret target you while you cause some damage to the opponent and let a carry dive to take them down while still dealing some dps, but out of it she suffers from the same Yorick does: Some potential, strong lane bullying with NOTHING to do for the team when the decisive moment comes, meaning she's not a very good teamfighter.
Some stuff could be done, like, reducing the time at which tentacles spawn, making tentacles not count as minions for the purpose of givine free stacks, give her E something as true damage, but capping it, and also making the tentacles carried by the vesel to span faster so it becomes a scarier desition to either run away from her or be damaged... I don't know, I'm not good with these balance purposals, but deffinitely, something has to be done about her.
"Please, tell me about your problems."