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.
Paroe1 votesThe 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.
MrSmothyFruty5051 votesIts not right always to do the proper rhythm to make the item work because it work's on xin zhao why not on aatrox its just not fair.
Paroe1 votesIts not right always to do the proper rhythm to make the item work because it work's on xin zhao why not on aatrox its just not fair.
Xin zhao doesnt have damage added onto the basic attack. He gets a heal every third hit. the phantom hit of guinsoo is hard coded to NOT deal damage. thats why it doesnt work with blood price.
MrSmothyFruty5051 votesWell its easier to not get guinsoo then :( .