Aatrox was buffed with last patch. Or more like "Aatrox was broken with patch 9.9".
"Riot removed the healing and shielding reduction on champions that Aatrox had on his passive. Instead, they have added healing he receives based on bonus physical damage dealt. Numbers on his Q and W are also being tuned, with cooldown resets seeing the biggest change. His Q’s cooldown will now reset only after the third cast of his Q or after the Q cast window expires. The overall cooldown on his Q will have its cooldown reduced and its damage increased. "
"Another big change for Aatrox will be the changes to his R. Killing him with his ultimate active will no longer revive Aatrox over 3.25 seconds. Instead, takedowns will extend his World Ender duration by 5 seconds and enable him to revive upon taking lethal damage while it’s active. He will also no longer fear nearby allied minions on R cast, and reviving him will no longer clear temporary buffs. Riot is further adding a hefty percentage of increased healing during World Ender."
May be they aimed to bring back a touch of the old Aatrox - but that version Aatrox was a glass cannon - while current version is far more tanky. So now he can sustain tons of damage (courtesy to the buff to his healing) - while doing tons of damage. Since this patch i keep seeing Aatrox being used for "free tower dives" and wining almost every fight 1 vs 2 (as a top laner - the turret dosn't help much vs Aatrox and if jg comes to help - both of you might end-up dead 2 vs 1).