AP assassins state as of now?

It seems like ap assassins are really hard to carry with (ahri aside). What with tanks being a pain to kill ( bruiser Fiora particularly in my opinion). Like during laning phase yeah sure you can get fed go 10/0 or whatever but when teamfighting phase comes actually "teamfighting" is very difficult without dying in the process. While they do have defensive items such as zhonyas and pretty good means of getting in and getting out whilst killing their target, (why is ms fortune so damn hard to assassinate when shes got an even score with me lol) actually surviving the fight or at least doing more than killing the squishy and then dying. My last 2 games were as kassadin and akali (both teams i was on lacked peel (unfortunately im forced to use team builder instead of blind draft because of how slow my in game chat is in champ select, and in team builder you can only be so picky))and i did well my self for the earlier parts of the game but could not find a way to actually be effective during teamfights or even carry even with how fed i was though my farm was meh. Later on in the game i found myself either dying trying to assassinate or going in and dying immediately after. Yes i know kassadin isnt the strongest ap assassin but i also lay and own others. I know fizz was nerfed not too long ago and while i do enjoy him its kind of a real pain that his only means of escape (E) is now a core part of his damage and most people are smart enought to move away from the troll pole. AP shaco is more about mindgames in teamfights and either way i feel like ad shaco is a much better choice. Other examples such as katarina (depending on how much cc the enemy team has there isnt that much you can really do especially if thier team is relatively tanky), teemo, who isnt THAT difficult to carry with but he does share his own problems what with his small auto range, ekko i dont play that much or know that much about, but i personally feel as though he is one of the few that carrying and teamfighting arent that difficult with, akali, (pink ward/reveal = less time to kill your target,) who's natural and added on spellvamp is usefull to keep her alive but teamfighting with her against a team with either wide ranged aoe spells, reveals, grievous wounds, or a good amount of hard cc seem to make me feel helpless as an akali player, is eve even an assassin now?, Leblanc, who from what ive heard her late game falls off, and i dont play nidaleee enough to give my opinion on how teamfighting is with her. Anyways, what im trying to ask is how are the ap assassins doing in LoL as of now? Are they actually still strong picks? is teamfighting supposed to be a weakness? or do they just rely on peel more than the ad assassins? My focus on this is primarily melee assassins because ahri can poke when she pleases. Id really appreciate the info. Alo its midnight so excuse the lack of grammar.