Why would you keep the Evelynn nerf?

Evelynn as we know it, hasn't been doing very well in the balance department. She's incredibly underwhelming now; to the point where people barely even use her anymore. And Riot decides it's time to nerf her again for the umpteenth time? Forty mana cost may not seem like too much for an ability to other champions, but with Evelynn's incredibly small mana pool early on, and with her relying on Q to clear jungle camps...she won't be able to use W as much, if at all, to get to jungle camps and lanes. Not only will this slow down Evelynn's clear time, this will also reduce her effectiveness in travelling to lanes and escaping, her niche.

You have stated Evelynn's niche before; constantly applying pressure to lanes. Now with this W nerf, all she has is her invisibility (which might I add; with the new ward trick being found, is very underwhelming now as well, in some cases at least.) As long as the enemy laners are smart enough, they'll know where to ward, how, and when to back off. There's been dozens of threads explaining why you shouldn't do this, but you've never taken an in depth look at them.

Sure, Runeglaive helps her a lot. But most of the time, you're going to run Warrior's anyway. Warrior provides Attack Damage, Cooldown Reduction, and Armor Penetration, all stats that Evelynn values immensely. Not to mention with an AD oriented build, she'll be able to get other smites aside from Trailblazer, and instead go for Stalker's Blade or maybe even Skirmisher's Sabre, which can increase her duel potential even more.

In reality Riot; at this point it feels like you just don't want to deal with Evelynn anymore, so you're steadily nerfing her to the ground until she's unplayable.