I really don`t like going Dark harvest mid, i think is wasted potential on Nocturne, also why do you choose to go for statik after your main Lethality? And Cull is really not worth for any case right now, i would only build if im behind early or i got early ganked, and i was low on money, but even then i would prefer building some longswords or Dorans Blade.

About the mid Matchups, Nocturne wins pretty hard against Fizz and Katarina but i agree with the Le Blanc though, its a pretty tough lane.