Evelynn has needed a rework for along time now in my opinion, and it's coming soon! She's nearly been the same since 2009!
Passive - Demon Shade:
After avoiding combat for a few seconds, Evelynn is enveloped by Demon Shade. If Evelynn's health is low, she'll recover it quickly while this ability is active. Starting at level 6, Demon Shade also grants camouflage—this makes Evelynn hidden from view to all except nearby enemy champions, control wards, and turrets.
Q - Hate Spike: Evelynn lashes out in a target direction, dealing damage to the first unit hit. If the lash strikes a target, Evelynn's next three spells or attacks on that target will deal additional damage. If the struck target is a monster, a significant chunk of Hate Spike's cool down will be refunded. After the initial cast, Evelynn can recast Hate Spike up to three times to fire a line of spikes through the nearest enemy. The spikes deal damage to all enemies hit. Hate Spike prioritizes the enemy Evelynn is attacking.
W - Lust Dust: Evelynn briefly curses a target champion or monster, briefly revealing her location to her target. Hitting the cursed target with basic attacks or Eve's other spells will expunge the curse, refunding Lust Dust's mana cost and significantly slowing the target.
If the curse lasts for at least a couple of seconds, expunging it will charm the target. If the target is an enemy champion, their magic resistance will be reduced for a few seconds. If the target is a monster, the length of the charm will be increased and the spell will deal bonus damage.
Casting Lust Dust does not break Demon Shade's camouflage.
E - Whiplash & Empowered Whiplash: Whiplash -Evelynn impales an enemy with her lashers, applying on-hit effects and dealing damage as a percentage of the target's maximum health. Evelynn is then granted a short burst of movement speed.
Entering Demon Shade upgrades Evelynn's next Whiplash into Empowered Whiplash.
Empowered Whiplash -Evelynn pulls herself to her target before impaling them, then deals Whiplash's effects to her target and all nearby enemies.
R - Widowmaker: Evelynn unleashes her demonic energy, becoming untargetable and decimating enemies in front of her. She then warps backwards. This ability deals bonus damage to low-health enemies.