Currently the only nerfs I think she needs is for her e to have a static cooldown instead of getting a lower cooldown per level. Max rank it sticks at 6 seconds with CDR items. Many of which are core on her.
The other major nerf I think she needs is her q should not increase her tower damage. She shreds towers faster than old fiora, old rengar and xin zhao combined.
I personally think her w deals pretty marginal damage, and rewards good positioning. its damage isnt anything absurd, but the slow is insane. Maybe make the slow scale up instead of being a flat 90%. Thats if we REALLY want to nerf her. Though the ability in general is balanced since you cant actually attack while its lining up.
The passive admittedly is pretty brutal in laning. However, it has a moderately long cooldown. As people play against it im sure they will learn its cooldown and play against it. It sorta averages itself out come teamfight phase due to teams mixed damage. I think the passive is fine. Vi essentially has the same passive but better.
There are dozens of champions that you shouldnt dive because of their ultimate. Trundle, tryndamere, J4, vi, vlad. The list continues. This ult is fine from my perspective since the enemies can just walk back into it. It has massive playmaking potencial because of the fact that she goes untargetable when the cast begins. Ive dueled a number of champions and managed to dodge garen ult, Darius ult, Riven ult, stacked Nasus q's. This ult has so much potencial outside of the core of its ability.
Her q already got nerfed, but it wasnt heavily impacting since she was meant to be an assassin bruiser. If we REALLY want to nerf this ability, make it so the true damage deals reduced damage to jungle creeps. Having an 800 hp smite late game on a 3 second cooldown can really shred barons, as well as make objectives have much more pressure.
Is she balanced? Kinda not really. But I dont think shes insanely busted or needs to be gutted. I feel she will become one of those champions with a bad reputation since she has a pretty unhealthy kit much like zed yasuo and riven. This review was brought to you by someone who is playing a ton of the new champion and absolutely loves her. Please riot, make sure if you do nerf her dont do that thing you do where you gut every single ability that isnt the problem, before finally actually nerfing the problem. Happy holidays :)