Nocturne needs some love.
Nocturne is so neglected in the game currently. He's called an assassin, even tho he plays like a fighter, so his base defense stats are absolute crap, making him unable to do his job as well as say a xin or vi could. He has awkward itemization, because you're supposed to build damage but he's so squishy that lifesteal isn't enough and tank on him just doesn't work great. If he's an assassin, change him in the assassin update. If he's a fighter, give him the base stats of a fighter so he can actually do his job without getting 1 hit. There are just so many champs that do his job better. Rengar, Vi, Xin, even Yi or Khazix. Riot can't decide if Noc is a fighter or assassin, so right now he sits in the middle with the advantages of NEITHER. He doesn't have the damage to be an assassin compared to the rest, or the tankiness to be a fighter.
TLDR; When you look at his kit, it's obvious he should be a bruiser, but his stats and natural squishiness make that very hard to do. He needs a buff to truly be a fighter, or a rework to make him more of an assassin in the assassin update. It's a shame such a fun champ sits so low in the tier list right now.