I'm not much of a Nocturne player, but when I do play him I usually build him more assassin like. Maybe instead of rushing the hydra as your second core item go for a more damaged based item such as a BORK. In my opinion it's better item choice as it gives you life steal, attack speed and some decent damage whereas ravenous hydra gives you tackiness which you don't really need as nocturne. Good guide overall though

Your guide is quite similar to many nocturne regular guide.Your core items are too weak. In S5, ganking & stealing is important for a jungler. If you buy Ranger, you will regret watching them get away with a few health left. Sabre & Stalker are much stronger and useful in either teamfight or solo. Hydra at early is also. Nocturne is squishy at early game,so damage means everything to him. I prefer BotR to Hydra since it deal damage on enemy's health percentage. Check my Nocturne guide, you may find smth useful.

I like your guide. Noc is a very underrated champ and even with all the buffs in s5 that place him at the same level as vi or jarvan he is still underplayed (tnak meta :( ). I would like to give you some tips as an experience noc player. First of all noc does have early AoE damage with his passive great for clearing camps. He doesn't need AoE damage in team fights because he is an assassin (even though some people build him offtank) as you said with his ult he can take down high priority targets. And my final recommendation. Don't build yomuu or rangers trailblazer. His passive gives him a lot of sustain allowing him to pick up the skimisher's saber which is much better for duels. The new black cleaver with the 20% cdr is far superior on noc since it gives armour shred + health + cdr.

Hope you enjoy