We all know Diana has been nerfed so hard you can't use her in lane anymore, and though she used to be a viable jungler most have forgotten her pure potential when it comes to jungling. You see this build and think, WTF, Wits end and Ferel, yeah it's not the best for AP champs, but when you have these two items, you attack speed is good enough so when you E them back to you, you can get of a stack of your passive for some great damage. And it also makes her jungle clear amazing.