I think the problem with his Q is how easily is to get interrupted. While Tristana's jump can be interrupted too, she is going to move away anyway. Aatrox will stay in the same place if he is interrupted during his Q. I'd add movement to his flight from the start, but that is just me.
I think his passive is just fine but i'd decrease its cooldown in higher levels. Aatrox feels really useful in teamfights with Sated Devourer. If they'd rework him in anyway, I think that should give them an idea of how. Maybe they could make his W react every 5 attacks at 1, and every 2 attacks when max, so it is less oppressive in lane with that high sustain but it is much more useful later in the teamfights where he should excel just because of his theme of warlord.