Eve would be a lot healther if she wasn't a jungler.
Her me out on this before the inevitable stream of downvotes.
Eve has a few core weaknesses in her kit that (are supposed) to make up for her permastealth. The first is that she has a distinct lack of CC. She only has high cooldown ult which is only a slow, so she's not supposed to tie her targets down very much. She has decently high mana costs on her Q and E which make sustained usage of them punishing early on. She has extreme vulnerability to poke due to her being extremely low ranged, squishy, and lacking in defensive steriods. She also has to remain in vicinity to waveclear, and is (believe it or not) weak in the early levels, with a power spike in the early-mid game.
Here's the problem; the jungle completely negaets most, if not all of these weaknesses. She isn't mana hungry early on because she's going to take the first blue, and because afterwards she spends enough time in stealth to regen her mana. She is given CC not only from red buff, but from chilling smite, which means that a fundamental weakness in her kit is permanantly removed. Poke is a non-entity in the jungle too, and her difficulty waveclearing becomes a non issue due to the fact that she can take down jungle monsters well. And you can't punish her level 1-4 weakness because she's safely farming the jungle where denying her exp and money is inadvisable, due to the fact that she can escape just fine (whereas in lane you could easily force her behind her own turret to miss out on cs).
Not only that, the jungle necessitates a certain standard of early power. You have to be able to survive the first few clears, so you have to have base stats that are decent. Because of this, riot hasn't touched her early skill's power, and instead hit her max level power. This causes her not only to remain extremely oppressive in the early stages of the game (because she does damage and can't be stopped from ganking) but it means that due to her base damage nerfs, she falls off like a rock when you hit ~level 12. And (as any skilled eve player will tell you) building straight assassin just isn't an option, not only because of the questionable viability of assassins in the current meta, but because she is too squishy with too low of a damage spike as well as low raneg to support assassination.
The jungle also allows her to stay completely hidden from vision almost all the time. It necessitates deep ward which are dangerous and require team coordination to function successfully (which isn't actually a thing in most solo queue games). All of this accumulates into a champion that feels extremely oppressive, but is backed by such lousy stats and an underloaded kit that, unless she snowballs her team, she ends up feeling like dead weight.
In a lane, however, her dynamic would be completely changed. Her Q can clear waves, yes, but in a posiiton where she's vulnerable to poke, and she is constantly visible. If she wants to drop into stealth, she is constantly losing CS, meaning that she is easier to track and the counterplay is much simpler: back off once eve has been in stealth for a little while, while the mid lane pressures, forcing eve to either miss CS or reveal herself. It also makes warding a bit easier, because the mid lane can pink against her rather than EVERY lane having to pink against her. By cutting off one lane (top or bot) you know that eve is going to the other one, thus giving you knowledge of her movement. Her lack of sustain would force her to be more adversarial if she wants to be successful, and would require clever manuvering of her W and her burst in order to win. She would be hard to gank, but let's face it, most champs who are popular are.
In my opinion, eve was designed (from the rework) as primarily a laner. The issue is, the jungle makes her far too strong, so she keeps getting nerfed (or maybe gutted is a better word) so that her perma stealth is quite literally her only strength. I know a lot of people are going to hate me for this next statement, but I think that if Eve were removed from the jungle (by reducing the damage dealt to monsters, much like they did to alistar so he couldn't be an issue in the jungle) then she could be balanced and allowed to be strong without getting nerfed every time her pick rate rises above 3%.
In many ways, I think this would actually strengthen her identity, not harm it. Eve is, to me, an assassin above all else, but she hasn't really been viable as one for a long, long time. Her base damages are just too abysmall, she needs defensive stats too badly. I never really thought that jungler was key to who she was, but assassin was extremely important to me. I feel like "fighter offtank" just doesn't fit her personality or her lore at all. Some people may think that she needs to be a jungler, and of course everyone is entitled to their opinion, but "Assassin who is constantly invisible and pops out of nowhere and kills you" feels a lot more toxic than "Laner who, if they ignore their lane, can go invisble and kill you at the cost of tower pressure and with a lot more warning beforehand".
And PLEASE don't cite the time directly after her rework when eve was sometimes played mid. She was so broken at that point that it is just not a good example. I remember being able to full/0 a fully stacked cho'gath with just my dfg and ult. There was a time when you could get her ult to do base of 60% max enemy hp at more than double the range it is now. She was overtuned to a really bad extent, that is not a good reason why all the previous analysis doesn't apply.
TL:DR The reason eve is so toxic is because the jungle hides her weaknesses, forcing a constant stream of nerfs that have removed most of her strengths (aside from the permastealth). She would be a lot more manageable as a laner instead, and it is my opinion that putting her there is (short of a rework, which I wouldn't advocate for because there's every probability she'd get the Mord or Cass treatment) is the best way to make it so she can be balanced.
Thank you for reading. If you didn't read, kindly do so before posting a comment about how I'm stupid. If you have read and still want to post such a comment, go for it.