Be careful when grouping up against him before a fight starts, as the more people he hits with his ultimate's initial hit gives him bars of his passive. If he currently has bars for his passive then try to back off and wait until it goes away, he can be very strong when his passive stacks up and that is how he gets his GA part of his passive, but it decays really quickly. He isn't really OP, he is actually very bad in team fights and really only good at 1v1s, and split pushing...at least in personal experience with playing him myself, though I'm no Aatrox main or anything.
You did have GW which is good, but your team was just way behind by the time late game came around, as the only fed person on your team that could of really did something against him was your Vayne. You weren't super far behind but you didn't really have much damage as the only AD item you really had was
and
.
In that particular game, you might of wanted to get
as they had 3 heavy auto attack champions, and maybe getting a
would of really helped against the Aatrox's Thornmail. I can't really comment on what you should or shouldn't do exactly as I'm only looking at the match history but I'm guessing that when you guys fought against the Aatrox, he basically jumped on and instantly went onto Vayne and after she died, you probably lost your chance to really fight him. Though your
probably could of did a lot against him, though he didn't build any crit so that might of also been the problem there as well.
I just think you were up against a really good Aatrox player, probably some one who mains them and knows a lot about his match ups and plays him correctly which honestly feels very rare lol.