Its been said before but saying it again.
Her utility is great with a possibly full team double shield that scales with her AP items, her burst is strong, snare isnt slow despite what people say and can snare 2 people, her ult does tons of damage with tons of range on a short CD even without resets.
And her E is very easy reliable poke and waveclear.
I was playing kass into her, at level 5 I had killed her once and backed and had double dorans and boots, she came back to lane with boots and some pots and still had her dorans.
My Rank 3 Q was doing like 1/6th of her HP. Kass passive has 15% magic reduc and i had one mr rune. Her E, without detonation, was doing about 1.5 times the damage of my Q.
So even if she was maxing E, thats way too much damage for that easy to land aoe ability with a slow.
She needs a tweak.
Snare should be single target, luscent singularity should have less base damage, and that ult needs a higher cooldown if she doesnt reset it - and honestly the reset should be much less than it is now and reset the same amount even if she kills 2-3 champs with it.
Is she squishy? sure. Does she have counterplay? Sure. But shes too strong for how safe a pick she is into any team comp and into mid or sp.
another idea to add some complexity to her gameplay is to reduce the base damage on her ult but ramp it up to the current passive + ult damage only if she applies the passive twice before ulting. So she has to land E and Q to get max damage ult. This way she cant zone you with E into Q and get full damage.