Yeah he is in need of a rework, a proper rework.
Any champion can be 'unfun', I don't see how a champion who does everything worse than other champions can be oppressive though. 'Boring'? Sure, he fights then sustains if he cans and then tries to fight again. That's what a lot of champions do. But he can't stick to you, can't burst you 100-0 without you reacting, can't sustain from 50% - 100% without lifesteal items or like 2 full waves of minions.
You're wrong about "Not need[ing] more in his kit", in truth he ACTUALLY does need MORE in order to function properly. But the best way to implement this is with a rework though, straight up adding power in his non-functioning kit basically will still allow him to maintain a kit and a half and yes this may lead to balancing problems.
Right now, he's not in a good spot. Meddler even commented on this and stated that he is not in a good spot, he might receive some changes before his rework sometime down the line but nothing is certain.
@OP; Aatrox needs a lot of things but just giving him things you want him to have doesn't make it a 'need'. He 'could' do well with tenacity but then his kit is going to have to balanced with tenacity in mind, and we know all know that one champion who we 'better nerf' because she her tenacity just could not balanced properly. Just wait and see what will happen, put some faith into Riot that they know where to take Aatrox next.