Ok i can confirm AP Jhin is a thing
He gets a huge AD scaling per level so i got 200 AD at level 18 without any single AD item. I got Lich Bane and Luden which gives me 220 AP~ My E dmg at level 5 is 255 base 305 AD 220 AP which is INSANE because he also has a great ratio on Q and his ult bursts like crazy (don't forget the passive).
If they keep the ratios as they are, mid mage Jhin is really a thing, praise @RiotGypsy !