It's his general kit that doesn't really work well with his playstyle.
You dive in with Q, and throw E, landing that you get a number of autoattacks against a melee.
If they are a ranged opponent you get kited and probably aren't going to land your E.
His Q shouldn't have such a revealing indicator for how difficult it is to pull off.
You don't get any benefits for landing your Q on it's outer circle. You get some damage and they get to run away. It should slow like all other abilities of its type.
His E needs a projectile speed buff and maybe even a range because you can't land it if they're running away directly away from you because Aatrox stand still while he's casting it. His ultimate deals a lot of damage and give him much needed Attack Speed and range, Aatrox needs some form of CC negation while this is active so that he doesn't get kited so easily. Something like a 15% Tenacity.
His passive is really bad because he has zero CC to keep people off him once he gets out.
He's not a Zac that can easily get out with a Q or and ult and heal tremenously while casting and moving. Aatrox needs to autoattack to heal and it doesn't work because if he builds tanky he deals no damage for the heal to even be viable. if he builds damage then he's not lifestealing enough to stay alive because of his squishiness.
His passive should give him something like:
Bonus 2/2.5/3.5% health per second and 5/6/7% decaying attack speed for 1.5/2/2.5 seconds for every enemy champion around him. This counter acts burst in team fights and this also means he isn't going to be OP in early 1v1s.
This allows him to tank for a few seconds after reviving and actually keeps him an impact.