Aatrox

I wouldn't say his kit is bad, it's just rather niche and a little hard to work with. In fact, Aatrox (played well) can be a veritable damage threat and a powerful split pusher, though he is also fairly easy to shut down in various circumstances.

Some advice:

• Know when to play aggressively and when to hold back. If you have Blood Well off cooldown, and are at 60-80 Blood, you're free to go aggro, but if neither of those two apply, hang back, and use your AS boost for farming instead of fighting.
• As a follow-up, know when to use Blood Thirst/Blood Price - damage is good, but when you have high attack speed (AS Items, Blood Frenzy, and Massacre), you may need to consider draintanking instead of chunking your enemy's health bars.
• Always try to use Massacre to supplement your 1v1 - especially if it means using it when you're sub-60 Blood and need to hit your Blood Frenzy.
• Also, be aware that you can't queue Blades of Torment or Massacre during Dark Flight. It's thrown me off a couple times, and I'm sure it'd do the same to you.