In terms of awareness. What doesn't the game provide anymore for assassins? %total armor pen. What does it provide? %Bonus armor pen and Flat armor pen. I understand that having 45 flat pen with zed at lvl9 when you get your youmu's is OP but that means you have snowballed and so, you are likely to win the game and that means that you have 19 pen in runes, like me, and you go for 18 points in cunning as you should do. But with others like yasuo, you don't have anywhere near as much flat armor pen. For talon, i would probbably use the same settup as with zed tho. ANyway, back to the point, what is the only item that works on total armor? Black leaver. What is that item's purpose? To lower armor and it needs stacking. Essentialy, if you need to stack something, you need time in order to do it. Assassins are supposed to work Fast. What does everyone have? Scaling BASE armor. What is the average base armor? 80? 85? What base armor do tanks have? 80-95. ADCs? 70-83. 88 if you play ADC kennen. So, with Base Armor values so high, you understand that if an assassin cannot snowball early then, in late game, killing "squishy" targets is impossible and with so many counter options to AD assassins specificaly, Assassins are indeed in a bad spot. For talon, you have GA, saling armor runes, heal and a support with exhaust. For zed you have flash, GA, scaling armor runes and of course this mothrfcker right here 
and as if it's active and it's 80 freaking AD wasn't enough, now it also has lifesteal, for -5 AD in expence... FUK MY LIFE.... For yasuo all you need is to play safe, have an exhaust, also get a mercurial and be with your support at all times. So, let's recap. High base armor values on squishy targets, no %total armor pen, very low flat pen values for late game, AD items like bloodthirster, IE, mercurial scimitar, essence reaver and such are nerfed and now have less AD, AD Assassins are indeed weak. An Assassin should delete a squishy carry both early and late in the game. I know, youmu's is a core and it is buffed but what did we get for it? No armor pen. MoM also has 10 armor pen now but it is not a core item, it is highly situational. A mercurial scimitar is far better.
So, come late game, all you have to do is get 27 bonus armor from runes and 50 from GA and with your base armor that ranges from 70-83 you have 145-158 armor. If you are graves, you get a shitton more with true grit.
Yes, we can get a black cleaver and still kill you if you don't have a GA but in 1v1 and still, there is high chance that we still won't. Black cleaver has no effectiveness on the first attack and to stack it you need to makemany attacks and in that time, the ADC with his/her high AS and crit will crit the assassin to death and that is not supposed to happen. If the assassin is a Zed, he will not kill you at all because you can cleanse his ult with your Merc. If you don't have merc then you are a dumbass and should lose the game. So, tell me, how is a Zed supposed to kill a draven late game when he has 81 base armor, 27 from runes, a phantom dancer and a Merc??? the answer is simple, he won't. If it's a talon, chances are he might succeed but that depends on your crit/as item. If you have a phantom dancer, his damage will be effectively lowered and your supp can have exhaust for him; Also, a good flash when he Es you can dodge a lot of his damage. Yasuo is the easiest. Qss his ult and hit him to oblivion. He can only dash to you once every 6 seconds, that's more than enough time, his ult armor pen only works on bonus armor and his damage is significantly lower with the same items. Also, 80% crit is not that much different from 100% crit. Didn't you know that you can Qss yasuo's ult? Well, you can't qss the knockup but his ult itself is not a knockup, it's a suspension and can't be cleansed. You will still take the damage but you won't be slammed down and you will surprise them, easily breaking their "flow" and action sequence and you will also easily dodge the free Q that he has after his ult. The more you know :P
Anyway, overall, AD assassins are in a bad spot, mostly because of the item changes. Most major high AD items used by the ADCs were also used by assassins and by changing those items, assassins got nerfed indirectly. IE, Bloodthirster, Mercurial scimitar and last whisper were items used by both classes. All have lost some AD with IE losing 15. The precious armor pen from lw was hit hard and it was essential mostly to Assassins rather than ADCs because assassins are meant to burst while ADCs can kite around. That's why the new lw items are good for ADCs but veeery bad for assassins.
I can't wait to see what items Riot will bring for assassins when the season starts tho. We will just have to wait.
, for instance are incapable of fighting them. There are several other tanks which you could argue that they can fight these Assassins such as 
, 
, 
but this is due to either their massive uncharacteristic damage or their high damage executes. (Yes I realize 
works too, but just pray to god they don't break him.)
