Why has aatrox hardly ever been touched?

Despite being released 2.5 years ago, other than a round of nerfs soon after release, he's hardly even had any meaningful adjustments. The last change he had was a scaling passive CD with levels. That was about 8 months ago. Before that it was that his ult fills his blood well by 20% per champion hit...

Other than those they've pretty much just been bug fixes. Yet this champion is so cheesy. His only real strength is that some people don't know how to play against him.

More specifically, what i don't understand is how aatrox has somehow managed to avoid ever getting any % damage or true damage added onto his kit.