I think Evelynn is mostly fine, people just aren't adapting very well to the preseason changes. She definitely seems to have a rougher first clear, and the increased price/nerfed AP on runeglaive delayed her powerspike, but her pressure and ganks are still awesome. You have to adapt to the role you need to be playing in your team a bit more now. Be it as an assassin, or more of a tanky initiater/fighter.
Vision has been a doubled-edged sword - green wards are less prevalent as the totem was nerfed and sight wards are gone, so there is less warding Eve's camps to keep track of her, but people are buying pinks a lot more.
Masteries: 12/18/0, pretty much always - with Thunderlord's decree - gives you some nice extra burst.
Damage items: 







Notes: Abyssal got 200g cheaper (so cheap wtf) so it's really great vs magic dmg. Some people like Rylai's as you can re-apply it really nicely with Q and it gives you some tankiness, some people hate it lol. Runeglaive + Rylai/Abyssal into tanky items is pretty good imo.
Tanky items: 



Notes: all decent options, good to mix and match with damage items.
And buy this
, helps a lot with your early sustain, which can be rough.