Alright...did some thinking, as I mentioned.
I sort of thing Assassin Eve has to vanish: the potential for a 100--0 burst out of stealth is pretty crazy. This is why Rengar takes a few hits to kill most people, and one of the reasons Talon had to lose his silence. I think that's fine: Hate Spike seems designed for a more sustained damage output anyway, and an Evelynn rework that didn't involve Hate Spike spamming would be an Evelynn rework that fails, in my mind.
So what if we positioned her as a high-damage skirmisher that pops out on an unsuspecting target and tears them apart over the course of several seconds? Sort of like a stealthy AP version of Master Yi? She gets her stealth, but she also gets to see her target live just long enough to experience the pain and terror of Evelynn finding them alone and defenseless.
With that in mind, here's where my thoughts went. I'd like to see the opinion of some Evelynn players as to whether or not this captures the feel of the character, and the playstyle you like about her.
Sadistic Glee [Passive]: Evelynn gains 4 / 8 / 12 / 16 / 20 / 24 bonus movement speed for 3 seconds whenever a spell strikes an enemy champion or Large or Epic monster. This effect can stack up to 4 times.
Where's her stealth?!? I know...I know. But you'll see that later. This passive change gives Evelynn some chasing power, and allows us to put another passive on Dark Frenzy, which you'll see shortly.
Hate Spike [Q]: Evelynn fires a line of spikes through the last foe she auto-attacked (prioritizing nearby enemy champions if she has attacked no living target in the last 1.5 seconds), dealing 40 / 55 / 70 / 85 / 100 (+35 / 40 / 45 / 50 / 55% ability power) magic damage to all enemy units in its path. Targets hit by this ability gain a stack of Hatred, which lasts for 7 seconds. Targets that reach three Hatred stacks are stunned for 1 second, and then cannot gain Hatred stacks for 9 seconds. Cooldown: 1.5 seconds
That's right...we're giving Evelynn a stun back. This one is back-loaded though: Eve needs a small window of time to activate it, during which a team could focus her down. Doing so reduces her "pop out of stealth and insta-gib you" power, which is really necessary. Hate Spike keeps its scaling into late-game though: you'll see a lot of AP ratio scaling on her kit, which lets us really scale her up to be a late game monster without making her early game too strong.
Dark Frenzy [W]: Evelynn passively deals 10 / 15 / 20 / 25 / 30 (+25 / 35 / 45 / 55 / 65% ability power) bonus magic damage on every auto-attack. When activated, Evelynn removes all slows affecting her, gains 30 / 40 / 50 / 60 / 70% increased movement speed for 3 seconds and ignores unit collision. Champion kills and assists refresh Dark Frenzy's cooldown. Cooldown: 18 seconds
The cooldown of the speed buff has increased slightly, but Eve's stun and ultimate will make up for the difference. The scaling bonus damage allows her to become the late-game monster this kit is designed to be.
Ravage [E]: Evelynn's dark magic strikes her target, dealing 60 / 90 / 120 / 150 / 180 (+75% ability power) magic damage and doubling her ultimate's passive attack speed for 4 seconds. If the target is stunned, Evelynn regains 25% of her missing health and mana. Cooldown: 12 / 11 / 10 / 9 / 8 seconds
This ability loses a little damage (until you build large amounts of AP) and a little cooldown, but now combos well with her Q's stun to give her jungle sustain and in-combat sustain.
Cloak of Shadows [R] [available at level 1]: Evelynn passively gains 20 / 35 / 50 / 65% attack speed. When activated, Evelynn cloaks over 2 seconds, for a duration of up to 10 / 12 / 14 / 16 seconds. She decloaks upon dealing damage, casting a spell, or coming within 500 range of an enemy champion. Cooldown: 80 / 60 / 40 / 20 seconds after decloaking
I know people are attached to permanent stealth on Evelynn, but, after thinking about it a lot, I just don't think it's good for her kit. Her gank threat is simply too high early on, or the stealth feels relatively worthless. By keeping the cooldown very high we can limit her early ganking power, which allowing her to use it more and more as the game progresses, becoming more and more of a threat as the game moves into teamfighting where her priority targets are more likely to be protected.
So...thoughts? Opinions? Is this an interesting take on Evelynn, or have I completely missed the mark? For reference, with 400 AP, Lichbane, and Nashor's, this kit can, at level 18, dealing about 1800-2000 damage in a 2 second window if left completely alone, which is up there with Master Yi. So you can think of this as a AP Yi sort of character: closes in on you when you aren't suspecting and, if you can't burst her quickly or escape, massacres you.