A few comments:
You don't go with maxing your CDR? I mean, you are quite reliant on alpha strike for your damage. I';d think you would want CDR to reduce downtime from 10 sec to 6 sec.
How about extra health? No Rod of Ages instead? Even with the reduced mana cost of Alpha, do you still need Chalice to have enough mana? You can't rush a catalyst and use that plus Dorans ring to have enough mana regen? I kept finding that Id alpha in, and then get Bursted to 0 before I could get away to Heal. Hence I took lots of MR as anti-burst and extra health from Rod.
I ask because my old AP Yi build was Dorans Ring, starting AP runes, boots, Rod of Ages, sorc shoes, Deathcap, Nashers Tooth, Abyssal Scepter, Lichbane.
I didnt play enough to really refine the build. The idea was Nashers = awesome CDR, decent AP, some mana regen, and the AS is actually useful with Wuju Style and his Ult giving him solid autoattack.