the problem i always find with Aatrox is that he has to build raw damage, while having his q and e the only cc. I still think his q needs a change because 1/10 of you hp for an engage/disengage is crap. ESPECIALLY the fact that it can be inturrupted by knockup or stun, high risk, little reward. Flat health costs are better imho than % like his w states. Secondly, his passive is still lack luster in late game, it just comes up earlier but still you die thanks to your entire team sacrificing you for the good of the team. Thirdly, he has 2 AS steroids passive and ult... which is kinda meh, because this means he can't have damage because he naturally attacks fast and that would be broken.
Personally I love Aatrox as a champ, but he needs ways to SURVIVE fights with people with pure stuns, knockups, dashes slows that are prevalent in the top lane. but changing any little thing makes him too op or not enough to make him relevent. because as is he either builds raw damage and dies in seconds, or builds tanky and can't fight anyone because the lack of damage.
I say give him the Mordekaiser treatment and make him a hybrid ad bot laner, buff up his base ad, change his ratios and abilities to assist duo lanes (COUGH COUGH ULT INSPIRING like his lore ), and change his sustain.
I see him more as a vlad fighter. So off the bat, SCREW the AP scalings, he needs to be AD or AP, and he really seems to dig into the AD side because Aatrox suffers from this because his ult does respectable damage, but it is just meh damage wasted unless you throw ap on him which normally gets shifty eyes all around.
I propose making him with a passive that gives his blood well and ties it to an ability W. so with every hit (skill or AA) builds the bloodwell up, and like
, out of combat it eats up the bloodwell for passive health regen. and w empowers the next AA and deals X damage on the next AA and only that one AA, and has 30% armor penetration for that Attack only. does not have a time limit you have to hit within x secs, but is a pure empowered hit guaranteed. Giving Aatrox a way to use his bloodwell 2 different ways, sustain while sacrificing csing or combat, or damage, giving up on the only sustain he would have now minus items. W no longer is what it was.
Q, change it so that upon cast you become invincible .5 sec after cast until landing, knocking up enemies in the center and slowing on the outer edge. making it Actually reliable as an escape or engage, and if not too much to ask, make it reset on kill. because he has 0 mobilty other than it 
has it, why not a top laner for once.
E, i think is fairly good in all respects and doesn't need too much change, its a farm tool i always find, and poke for a melee champ.
Ult HOOOO boy does it work decently at times, but in others it's just meh, instantaneous damage upon cast (AP), change to a lower ad value, Range increase fine, AS buff fine, but i would like to see if they can buff it to give him the ability to buff an ally too, jungler/support(if that were to work) through giving allies and only allies some aura that can increase either defenses, or crit chance, or something that ties into his lore inspiring people to fight on against all odds, becoming more than they normally are. Even buffing minions would be an awesome help. buffing minions isn't something that has been done really.
But Aatrox I find always seems gimped in every matchup because he is an all in champ that hurts himself to do damage, and has no survivabilty in large cc comps that are everywhere right now that easily shut him down.
still has him beat in the lacking usefulness category but yeah i feel you, when i see an aatrox i never know what to expect he is jsut too unreliable at the moment to have an idea of what he is supposed to feel like.
