[{quoted}](name=Justicar Aatrox,realm=OCE,application-id=Ir7ZrJjF,discussion-id=MPLpspyZ,comment-id=000e00000000,timestamp=2016-12-16T00:59:04.683+0000)
Except most of the time, you can fight him.
Except they never really touched his base stats.
Except they didn't touch his ratios.
Here is the link to his balance history - though I bet you won't read it and continue to make up crap anyway.
http://lol.gamepedia.com/Aatrox_-_the_Darkin_Blade#v3
Here is his context to his 'biggest' nerf: Any champion can be frustrating to play against when they’re capable of building very tanky while still outputting considerable DPS, so we're lowering some of Aatrox’s innate damage. With this change, Aatrox must build items for damage and won’t be able to simultaneously tank and smash face as easily.
Basically, he was pulling an Tankko. But guess what, unlike Ekko his damage fell of hard late. Unlike Ekko, his doesn't have infinite mobility and incredibly wave clear. Unlike Ekko, his 'get out of jail free' still got him killed if it was popped. Not once did it mention about his "impossible to 1v1" or "insane lifesteal". They didn't even touch his W.
Aatrox was never this "broken feast or famine duelist" it's just how people wanted him to be remembered. His W sustain is on a 3 HIT PASSIVE. It doesn't scale well and he has to choose between doing more damage or healing for a bit. Do you know how much attack speed he actually needs to be able to proc his sustain that often? And do you know how much bonus AD he has to forego to be able to obtain these attack speed items?
Let me list a few candidates who are not only strong duelists post nerfs, but are either able to keep up or outsustain Aatrox:

With and without items, all these champions here have strong sustain mechanics. If you've played Aatrox against them and both teams got to late game, you would see more or less at the end screen that you would have done similar amounts of healing.
Tl;dr - So, if Aatrox is o/p because of one ability, his W Blood Thirst, how is it that other champions with overall better kits can keep up with his sustain and are able to build tanky whilst he must go for ad/as/ls in order to have relevant healing?
P.S: Here's a clip of SEASON 3 Aatrox, aka Pre-Nerf Aatrox (his nerf happened on the 29th of October, this footage was uploaded on the 26th) vs a non-lifesteal build Warwick. Aatrox gets straight up destroyed in a lifesteal fight one that you seem to assume he was king in judging by the way you pose him as this "impossible to 1v1" character.
https://www.youtube.com/watch?v=iaQ4yczWc7Y
Eh, just using what I've heard over the past, say 3 years or so. I've not much idea what nerfs he actually received, although mostly I've heard talk about how his double healing under 50% was a problem (I remember going into the jungle and hitting old wraiths 3 or 4 times and healing back to essentially full, which can be compared with the healing capabilities of a lifesteal Riven build or something, except that Riven has low AS. Not sure about the comparison to Xin and WW, though. Xin's heal is based off AP, however, so I think it may fall off late game.
Anyway, clearly 'Any champion can be frustrating to play against when they’re capable of building very tanky while still outputting considerable DPS, so we're lowering some of Aatrox’s innate damage. With this change, Aatrox must build items for damage and won’t be able to simultaneously tank and smash face as easily.' doesn't mean anything anymore, with Olaf getting 2.5 AS with just a Bork at practically full health (iirc, S6 this was).
Other than that, Xin has a three hit healing passive as well, and Aatrox's sustain outmatches any one of those with his lifestealy build(well, used to be, am seeing people use other things now), which makes up for no damage on his healing form, while his damage is higher than Irelia's against squishies, although I don't know how an AS speed works against a damage boost, but with Aatrox's ult being more powerful duel-wise, Aatrox should be able to hold his own against a Xin as long as he as a full bloodwell and doesn't get his Q interrupted by Xin's knock up.
Fiora's essentially a better drain tank than Aatrox ever was, sticky but low range, and almost entirely single target (less than Aatrox anyway, he has about 600 base damage in AoE). The thing is, she is terrible in teamfights, so there's no '5 people focusing 1 person who just sustains it all up' type of reaction (no that's not literal)