I use Aatrox as one of my main top lane champions, i have tryed him in the jungle, it works, but it wasnt my style, but i should try him again, but since i only know about him on top lane i will only talk about top lane.
Aatrox can be built as any of the 3 meele roles and still be useful, you can build him as an assassin, if you go full damage, as a tank, if you go full defensive, or in the middle, with a bit of damage and defensive, being the "middle (fighter) what you will do in the majority of your games. Your build is decided by 2 things, first, how you are doing in the lane, if you are behind, you will have to start with defensive items (raundins or spirit visage) and if you are ahead you can start with the damage items (blade of the ruined king or ravenous hydra, depending on your enemy). Past that point, it depends on you team, if you have a fighter or a tank on the jungle or a support tank you can build some more damage, but if your team doesnt have any other tank, you might end up having to go full tank, and believe me, this will happen more often than you think.
About him being early, mid or late game, he was made to be a late game champion, but from my experience, he is strong in the early, mid and late, while never being exceptionally strong or weak, his late game is weaker than that of a jax or irelia, but his early game is stronger, and his early game is weaker than that of lee, but his late game is stronger.
Hope i helped