Context on Viktor nerfs?

Seriously, why is Viktor getting a nerf? I don't see him played that much, and even when he is, he seems perfectly fine. Looking at champion.gg, none of his statistics really jump out at you as being over the top. In fact, statistically it seems that he is a relatively weak champion, with even experienced Viktor players having an average 49% win rate. He does okay in pro play; he doesn't dominate the competition by any means. I would like some context on why we're seeing a nerf on him, especially to his main damage source.

Meanwhile, champions like Lux and Ahri who are consistently stronger at just about everything remain untouched. I just don't understand the logic Riot has. Are they seeing something I don't here?