The state of Evelynn's Kit and Hybrid Champs
Evelynn is in kind of a bad state right now. Part of the problem is her kit (her passive is a discussion in itself). Half of her damage is physical and half is magical. For some champs, this wouldn't be a problem, but for an assassin, it is very much a problem.
First is do you build AD or AP? Hybrid items suck (getting back to that). Most players have to choose either/or. Evelynn, I don't think she can.
One of biggest issues with hybrids right now has to do with penetration. There aren't any good penetration items for hybrid champs. First off you'd need both a void staff and a last whisper. Getting both of those on the same champ, unless that champ had insane base damage, isn't going to work out. Neither offers much damage by themselves.
Percent penetration when you aren't scaling that well doesn't work too well when the champ you are laning against is getting 250 armor and 250 mr and bought a bork. Even with 33% penetration that's still 60% damage reduction as well as a lot of health gain.
Evelynn needs both kinds of penetration for her kit to work but as it stands, I don't think she can build either kind. The penetration items don't offer much in the way of stats. Gunblade sucks, can't buy that. TF is nice, but doesn't offer a lot of any one thing. It needs you to build AD for the proc benefit as well. It almost wants you to build raw AD.
Evelynn needs to build AP and speed items for her Q to kite with. Her E needs an all in built and tank. Her W doesn't do anything for damage directly. Her R is limited in usefulness and it gets worse the later in a fight you decide to use it. It wants you to initiate when assassins are generally clean up. Katarina is a good example of this. Your team gets the other team low and she jumps in and ults. Evelynn's passive has limited use in a fight once she's engaged. It's nice when you want to avoid a ward, but when you are actually fighting it's not much help.
So basically her bloody kit is all over the place.
While I'm focusing my discussion on Evelynn, building hybrid in general is something you can't do very effectively right now. Kayle only builds AP. Akili isn't that popular. Kog usually only builds AD. MF and Irelia have AP scaling, but you never build them hybrid, it just sucks on them. Katarina only builds AP. Yi got nerfed so he can't build AP anymore. Because of the way being a DD works in the league now, you have to have penetration to have any hope of dealing with a tank. Most hybrid champs are DDs. Just by going hybrid, you tend to be hurting one stat or the other and then there's the problem of penetration. You can't justify both. If you do get both items, you've gimped your build so hard because you don't have the numbers to take advantage of the penetration. If you build neither, you aren't going to get through the 80% resistance the enemy's tank just built and your ult just bounced off of him. Most tanks won't even feel a loss of 5% tops of their health.
For an effective DD you almost need 500 points or more in one of your damage stats and 40% penetration. Eve is a DD but she can't really build like she needs to because of the way her kit is pulling her apart.
Itemization for the league really needs a bit of help, particularly for hybrid champs.