That sounds like more nerfs than buffs. Illaoi has the issue where she brings nothing to the team. Currently all she's good for it beating players who don't understand her kit and play against her all wrong. She needs a big increase on her slow, like turn it into a stun or a 99% slow that lasts a long time if they leave the zone. Or give her some speed. Anything to help her stick to a target or engage, or offer utility.
She needs something to give her a reason to be picked other than just damage. Illaoi is a tanky/high damage CCless champion Like Shyvana, but without the speed to stick to people, so everyone just calmly walks away while she does nothing. The other juggernauts (like Garen) have speed, or a hard CC/engaging tool (Darius) and I feel like Illaoi needs more than that very brief slow that usually activates when the enemy is miles away from her. She needs... some utility/niche/purpose.
TL;DR: She's frustrating to play against but not a "strong" champion. Fix the frustration without nerfing her. Give her some sort of defining trait/a reason to pick her.
The buffs like faster tentacle spawns are wonderful but there's so much more that needs to be done. Like her vision issue ruins her. People can see tentacles perk up when she goes near them, even in fog of war, and that gives away her position. Because of that she will never be in competitive play and will never be viable against an aware opponent. She's really only effective (but VERY effective due to her confusing nature) against inexperienced players.
Honestly I would have been fine if you guys just added more visual cues to her E. Most people see the circle and assume "I need to get out of it." If you put a giant arrow on Illaoi or made the circle look more like an arena you want to stay inside, or make the outside of the circle look red/evil/bad then people would understand to stay inside it and kill her.
Also It's also only a "trap" if she's level 6+ and has her ult. Without her ult going ham on her seems fine.