@Riot Meddler: I Told You!
So, I posted this thread. I addressed all the problems with this nerf. I made it VERY clear that this was way too heavy to shift in one patch without compensation buffs.
Aurelion Sol is NOT an Irelia case. He is NOT a Malzahar case. He's DEFINITELY not a Zed case. He is a very rarely played, almost never banned champion that the meta favors right now. That is not grounds for such a devastating nerf to BOTH his early and late game power, it's grounds for shifting his power to a source that is less binary; instead, you've made Sol even MORE binary: You're fed enough to win a fight before inevitably being CC'd or having your stars ducked inside of, or you die.
DO NOT revert the W nerf, do NOT reverse it until you see his winrate where you want it- rebalance his UTILITY. Suggestions: Slightly increase his base health and move speed. Rebalance E to stack slower but have a 1.5 second delay before losing speed, stacks, or flight, like Malzahar's new passive. Remove Q delay. Reward nurturing Q- start CD on CAST, like Fiddlesticks; pre-buff, but increase the CD 1 second at all ranks.
Your design team made a mistake putting so much of Sol's power into his W, BALANCE him by distributing it more evenly. This will also create an influx of players- so his winrate will reflect what he can do, not just what Sol MAINS can do.
Edit: I answered some important misconceptions about Sol in the comments, here you go: Sol does not already build tanky, he builds Health. Mitigation items are weak on him because of his low base health, tank items like Sunfire are weak on him because of his low in-combat movespeed. Increasing his base Health would make building mitigation on him slightly stronger, and in turn encourage build diversity over 'stack health and AP'.
A 1.5 second delay before losing stacks, LIKE MALZAHAR'S PASSIVE. When Malzahar takes damage, his shield sticks around for 1 second, then drops and goes on CD. Same for Sol's flight/stacks, they linger for 1.5 seconds, after which you're back to 0 and the ability goes on cooldown, if you were in the air.
Removing/reducing Q delay gives HIM counterplay against certain types of champs. His only counterplay is NOT hypermobile champs that can sit on his face forever. Those are just the champs that make Sol mains drop the champion after a few in a row. As a Sol player, there is NO counterplay to this happening to you. It's binary; if you don't have ult or flash, which SHOULD NOT be compulsory anyway, you have zero hope. This is your life now. You're dead. That's not healthy champion design.
The Q changes DO fit together, however; 1 second increased cooldown means when you double-tap it, it's actually on cooldown longer than it was before. This breaks the unhealthy 'win more' nature of Sol's Q in a 1v1, pushing it more toward being an all-around tool of his kit. Initiation, peel, or sticking power- but not all three. Starting the cooldown on cast also adjusts the power of the ability based on how it's used- if you use it to initiate, you're no longer helpless for several seconds immediately after that flashy EQ play. If you use it to peel for yourself, you have to run further- and since your stars are probably in and on cooldown, turning around fights is a much riskier play than if you had flash or ult up.