Giving Olaf's passive to Aatrox has been suggested before but It took me a while to fully agree
(Inb4, Instead of thinking of it as something being taken away from Olaf, think of it as a chance for a much better and interactive passive for him, as well as improving Aatrox.)
Took too long but It finally makes perfect sense to me.
Olafs Passive alone is very bland, and he could Imo definitely use a new one, but if you took that Passive and tied it to Aatrox's Blood-Well I think that would fix most of his problems.
Currently Aatrox gains attack speed based on stored Blood, but It's really a pain in the rear to micro manage it, relying on perfect ultimates to fill or being limited to split pushing all game so his well stays full.
Now if we un-tied the attack speed from his Well-percentage, we could then tie it to his current health % like Olaf, which really suits Aatrox's kit much better, considering all of his basic abilities inflict self-damage and he can resurrect.
One of the biggest Issues I have with Aatrox currently is how he loses his attack speed when his blood well resurrects him, what is the point of a telegraphed rebirth passive if your whole kit requires ramping up power and costs health but you res with low health and much less attack speed?
If Aatrox had Olafs passive un-tied from his blood well, he would actually be relevant after he resurrects with low health.
This type of passive would enable Aatrox to participate in much more teamfights because his attack speed is always available depending on his health.
Sorry I know this post could be more effective but I really hate how neglected Aatrox has been forever and just had to suggest something..