The one thing I feel that holds Aatrox back the most
Is his vulnerability/attack speed loss after resurrecting.
Aatrox needs to be smacking things repeatedly to have any chance in fights, but his weak rebirth is extremely telegraphed and drains his Blood Well which costs him a lot of crucial attack speed.
Aatrox is super reliant on attack speed and without ultimate to instantly buff it his kit is very weak, so resurrecting is often just going to result in death again.
I propose that Aatrox passive retain it's blood well through resurrection, so he can actually make use of his "free man".
The heal would still depend on the pool but not cost anything.
90% of Aatrox kit is his W, so to resurrect with minimal attack speed and low health is near pointless