Instead of nerfing rageblade's %AD/AP stacks, just make its %AD/AP mutually exclusive with dcap
The issue is arguably that buying 225 raw AP (rageblade+nashor's+dcap) ends up netting you almost 400 AP with a stacked rageblade because of all the multipliers involved. The efficiency is too high -- and that's before any gathering storm stacks kick in.
If the issue were rageblade itself, then arguably, kog should be an issue too; but he's not. The issue is champs that go rageblade>nashor's>dcap. So nerf that buildpath instead of the rageblade itself, imo, then see if followup is needed.
Also, looks like we're hitting kai'sa with the classic nerf the champ>nerf the item>leave the champ alone lul