Mid game aatrox is a hard thing to go up against when it is farmed and ahead. Although it can be shut down by a single fed champ. to make sure you receive the most out of your champ and its abilities take red buff whenever you can and make sure you pressure the enemy jungle. The rest of the mid game will be on your ability to make plays and smart decisions.

NOTE- Go for dragon whenever you see a good time, Aatrox is amazing at taking out dragon early.

Aatrox is a champion where rushing flare is a good idea while maintaining your ganking ability.
Early game start red buff and move towards wraiths. when you have completed wraiths move towards blue and wolves, then gank either top or mid lane depending on lane pushing or who needs one. Then start working towards your Blade and Boots. Another thing that is goes good with Aatrox that I didn't included was Youmuu's ghostblade, the reason being it is meant for Aatrox top lane, but is also effective while jungle ganking. I would only consider purchasing this item if you are very far ahead and your team is doing well.

Aatrox damage falls off slightly late game, but what balances him out is his attack speed. late game aatrox all depends on 3 things.

You- how well you are doing and how good you are mechanically with this champ.

Team- how well your team is doing.

Your build- if you build correctly you will have no problem taking the game provided all 3 things are taking place.