Even ignoring balance, the PBE Jinx changes are going to be a negative QoL change for Jinx players
Her AS is all over the place all the time to begin with -- now it's going to be even more inconsistent than it already was. Missed autos ahoy.
And no, I don't think the nerfs are justified. You just nerfed Cinderhulk, and Cinderhulk meta is arguably why her winrate shot through the roof. Give assassins and champs capable of diving the backline a chance to rotate back into the meta, and then evaluate where she stands. She's a carry with a strong midgame who gets an amazing steroid in exchange for divability and poor range with said steroid; I don't think there's any need to nerf the steroid because its inherent weaknesses are -already- incredibly strong.
I could complain for years about this, honestly. I am not pleased. The change will feel bad to play, and it doesn't make sense to me, either. Jinx sees little in the way of competitive play for a reason, and it's because she's an immobile rock that can only deal hypercarry damage at 525 range after a mediocre early lane. She's not bad, but her kit carries significant risks that are only mitigated if the enemy team isn't able to counter her with their teamcomp (and the enemy team can always be made to be a nightmare for Jinx unless she's essentially a last pick). Furthermore, other champs all fill Jinx's niche better in organized play. (Trist for pushing, Kog/Vayne for hypercarrying in Juggermaw-style comps, etc.) Don't nerf Jinx because she's strong in solo queue, where both teams are busy playing Game of Throws and making bad choices at champ select.
And hell, nerfing q like that takes away Jinx's unique niche and powercurve as a midgame powerhouse. That's just dull. If I have to wait until lategame to scale, why should I bother picking Jinx? Other champions do what she does with either more damage or more safety (and sometimes both) by then.
Basically, the changes will feel bad, will likely be unnecessary once people have explored the meta post-Cinderhulk nerf, and will damage Jinx's identity as -the- AD with a midgame/level 9 powerspike. I do not like them.