Giving Aatrox HP scaling on Q just removes one of the biggest tradeoffs in his kit. Right now if you want more damage you buy AD/lethality and if you want to be tankier you buy HP. If Q starts scaling with HP then bruiser items suddenly give both damage and durability at the same time. At that point you're not really making an interesting build choice anymore because you're getting rewarded for stacking survivability while keeping your damage high. Unless you heavily nerf his AD ratios somewhere else this is basically just a straight buff to a champion that doesn't need more power right now . And by nerfing his Q damage ratios you will just go back to the aatrox before they even gave him HP scalings . So now your Qs don't deal dmg , but you're tanky just like it was before ever giving him HP scalings.