It's just a straight nerf for a champion that is already not viable in competitive play and also not problematic at the very highest levels. It's a SQ problem more than a WW problem. He needs tweaks not late game nerfs. To nerf his already weak late game would make him so all-or nothing that it would feel like the whole game is a dice roll if the enemy team is safe early on. Such a champion is almost never attractive higher up because it basically requires snowballing to have relevance and you feel powerless if the enemy team hasn't made large mistakes.
Plus, despite randomizing the game more if it goes later, a Q nerf actually does not really address the reason he's successful in SQ. That falls mainly on his W movement speed. I thought yesterday's changes with the Q damage/healing nerf early but better scaling were good except that the W movement speed early on wasn't nerfed enough. 25% is still a lot at level 3. Starting at 12-15% for level 1 W seems like the better option. I also wouldn't decrease the W CD.
I'll just post my previous thoughts on WW:
"I'm not convinced WW needs any nerf. He's a champion designed to exploit SQ players even when balanced and I don't think people itemize great vs him either. He's a menace until players get much better. People don't like to have to adjust their play vs champions like Rammus, WW, Nocturne, Rengar, Zed (not sure of his current state) etc. but that doesn't mean those champions are actually out of line. This is probably why WW has a worse winrate in KR despite a far lower pick rate. He's also only banned 1% there but has a 40% ban rate here. WW would be picked in competitive if he were objectively strong. He has seen virtually zero competitive play since release.
Moreover, while he has some tricks, his skill floor is quite low. In fact, WW actually guides you to the decisions you should be making as a jungler via his passive and reduced farming ability till Tiamat. Tiamat is a lever on his power but the problem in SQ is that he gets it quite fast since people give him early leads he shouldn't have. I think playing WW literally makes you a better jungler if you're not particularly skilled at the role. Since he's a good duelist, he can also snowball his lead well. Some champions will just have higher than average winrates for most of the ladder when objectively balanced. If he drops to a 50% winrate in SQ for below Diamond with his current kit, he'll probably just be unviable in Masters+. Thus, I don't think any nerf is required but perhaps there can be some tweak in his power. Maybe angle some power away from early and add it to late game (the old WW was better late game).
One way to do this is to nerf his W passive early so he can't get fed as easily vs bad players. Another reason to do this is that it has become the best max order and nerfing this might give the option to max Q first instead (though probably not in 95% of cases). Furthermore, the best WW players tend to put only 3 points into W early and then max Q followed by E. It seems that they use it to snowball early but don't find enough benefit in putting more points relative to getting tankier from the other max orders. An example of how this would look 35 / 40 / 45 / 50 / 55% -> 12% 24% 36% 48% 60% Having a larger difference in each rank would make W maxes more meaningful and an actual decision even after the early snowball phase. It might also make top WW more viable since he can split push and then use the slightly better max rank W to join his team faster. WW's not a great late game champ right now (outside of bad play which allows easy picks or in skirmishes) and this would help him a tiny bit there. It would also make Deadman's more attractive relative to just full tank with Randuin's. Overall, I think it's a net nerf for all tiers but it nerfs bad WWs the most. They'd have to consider the situation more and show up where they need to instead of just relying on the passive early to get fed and snowball, then get Tiamat, power farm -> dragon etc. For good WWs who know where to be and how to jungle in general, the nerf is less severe so I think this would hurt the highest MMRs less."