"AP champions are weak"
EDIT: the only argument I can see for ap champs being weak is that Yasuo, Irelia, Zed, and Talon all have relatively high pickrates (11%, 11%, 9%, and 6% respectively), but they're the only four AD champions out of the top twenty.
Let me post a counter argument here.
The jungle is primarily dominated by AD champions, right? Not exactly.
3 out of the top 4 are exclusively AP. 4 out of ten total (or just 3/10 if you don't count gragas which I personally don't because champions like him, Zac, Sejuani and Amumu are picked mainly for their CC and tank above anything else). There are only about 6 or so AP champs picked jungle in total.
Those numbers are very comparable to the top tier AD mid champions. Why aren't people asking for AP junglers to be taken down to a lower level?