Well it is a build guide and since your items are the main part of your "build" I feel a down vote it apropriate. If your trying to rush one Item at a time i could see how malady is a faster route for you in witch case would make sence. If your a skilled Diana player though you wont have any trouble getting the higher tier items. I also dont agree with your rune choices either since Diana has great base AP and AP scaling theres no need for anything but AP quints so getting MR glyphs and Armor Seals would be a better choice.
My overall point is there are better item and rune choices based off of not only my play style but what ive observed from other players

p.s. I notice my build now has a down vote without an explination wich was resived today right after I voted on your page. If this is how you take critism your not going to get honest ansewer from your veiwers due to the fear of negative retalition votes. Now that being said, if you have real reason for the downvote plz leave a comment and Ill be glad to discus it with you.

I get Malady because it's far cheaper than a Nahor's tooth and you need the AS very early. So Malady is the way to go. You dont need MR runes if you get Abyssal Scepter. And I prefer Rabadons because you get far more ability power from it and due it's passive. but nice to downvote just because you dont like the items, like you do on other diana guides, what I saw on your profile.

Too much AP. Since you spend most of your time in the middle of team fights you need more durabilaty.
I would only get AP Quints and change your Glyphs to MR per lvl. I would also get a Zonyas vs a Deathcap for its armor and its passive. As far as AS goes I agree with you as far as runes but I would get a Nashor's Tooth vs a Malody.

I take AP runes because i'm getting Rabadon's Deathcap as my last item, so some early AP are good. I added a jungle route picture and also some of my stats

I take the AS because her passive gets very strong at the end. And RoA is a must have core item on diana because she is really mana dependant and needs a high survibility. Playing her full ap is the worst thing you can do.

You don't need that much AP runes, Mark of Magic Penetration is a great choice, but you might wanna change your Seals and Glyphs runes. You need more pictures and a picture of what the jungle looks like, to show people your route and etc etc

Sorry but I don't like to build her with Attack speed and she doesn't need AS runes on jungle cause her q,w do so much that she doesnt really autoattack after few items, Same with RoA on her, i like to play her almost full ap heres my guide please check it out still doing it :/ = My Diana Build/guide