Not necessarily, Evelynn sill does a lot of Physical Damage from auto attacks. I don't know about AP Evelynn, but I'm pretty sure AD Evelynn is the only one played in the LCS and was proven better, due to her making much more use out of her E, her Q scaling being the same, and the fact her ult's AP scaling isn't really that noticeable.
The enhancement actually works on Evelynn probably better than a lot of people who get it, the 10% CDR can be utilized by Evelynn much more than most other Warrior-Junglers, due to her spammy style. It works really well with her kit and the extra Attack Damage and Armour Penetration just add onto her auto attacks. The entire enhancement is at least, better than pretty much every other enhancement at the moment on her. Seeing as the Runeglaive one is for AP, and AP Evelynn just isn't as strong as AD Evelynn simply put, there is no reason to choose it. The only other viable one would be Cinderhulk instead of Warrior, due to it making her more tanky. But Evelynn isn't necessarily a tank, she's an assassin. I don't see a problem at all with building her with a few tank items, however she is still all-in-all an assassin and she won't ever match up to the tanky CC gods like Sejuani, Gragas, or even Malphite.
Also, Evelynn doesn't really have any mana issues due to her passive mana sustain. Even if she does, blue buff gives her more than enough and past early game I don't think I really ever get out-of-mana with Evelynn.
Armour Penetration, due to the fact that Evelynn does have most of her damage from auto attacks, is still pretty good on her, but it doesn't change anything about also building something like Sorcerer's on her, since she does both Magical and Physical any penetration will noticeably work.