Reading too far into the W cool down change is not the only thing that gives that impression, the nerf to his passive late game from 4 seconds to 6 seconds is absolutely insane. I thought the design plan was to make Ryze a monster late game, and his early and mid game extremely weak. But with that change, Ryze is significantly weaker at all stages of the game, making him significantly weaker than other counter parts you can pick top.
That being said, I saw the changes implemented today, and they seem to be heading in the right direction. The W looks like at max rank, it will still provide some utility without being absurdly op like before, which I am perfectly fine with. 5.10 Ryze was disgustingly op due to a lack of hindsight from the development team.
However, I am still worried that now there is not purpose for Ryze being picked anymore over other options. With his nerf to his passive, he has no real late game high moment. With this nerf to his pattern, and the fact that Ryze cannot build tanky anymore, there is no real reason to pick Ryze over other strong top lane picks at the moment. Vladimir is an example of a champion who does good damage late game while being tanky, and has the tools to survive top lane in the early game.
Those two seconds on his passive really need to be added back into kit, implemented like they were in patch 5.8-5.9 where it scaled from 6/11/16. to a max of 6 seconds at level 16. This will ensure that he can continue to use the full power of kit late game, but it's at a stage of the game where the enemy team will be able to have the items and scaling to be able to deal with it, and it becomes a match up based on skill, and team comps. Ryze should be able to become the strongest of carries late game, and outscale his enemy. 4 seconds is too short of a window for a champion like Ryze to be able to excel, and he will most likely be left in the gutter changes are not made to this area of his kit.