Riot games 
is bugged on some champions. For example i give 
sometimes it works but when it doesn't you are screwed. So when you buy it on his W doesn't work sometimes and you die because of this. Please try to fix this bug.
The reason it doesnt work is because aatrox blood price adds physical damage onto the attack. the phantom hit DOESNT do damage. its hard coded not to. thats why it doesnt proc cleaves from tiamat and ravenous hydra that do damage, but procs titanic hydra and other on hit effects.
You just have to make sure youre always on the proper rhythm. it is kind of stupid, but theres not much you can do about it since blood price is a non-standard effect.
