As someone who plays Quinn A LOT, I tend to find the rework of Quinn to be pretty depressing. What really kind of irritates me with ult (and really the rest of her kit) is they have put forth this idea that your choices should all be "Meaningful" and that was what they stripped from her kit.
"Are you past level 6 and moving while out of combat? Ult you fool."
That's really it. That's not a choice, it's just a mandate. If you aren't doing that, then you're bad and you should feel bad. She also has this particle effect that happens when you end your ult. They like to call it "Skystrike" but really it does literally nothing anymore. Might as well switch the particle effect to confetti for all it matters. But hey now you have a new skin "Surprise Party Quinn."
Truth is thought that her old ult wasn't amazing. However, what it did offer was a meaningful choice. If you split pushed you could ult to push the tower down faster, and likely die for your effort or save it and use it in a multitude of ways: Do you try to use it to run? Do you use it to make them believe you've run and then dive back in when they won't expect it? Do you keep pushing or use ult to get to the team fight? The question was How bold do you want to be? There are about a dozen more ways I'm not mentioning but really that isn't the point. The point is that the decisions were real and meaningful.
The problem is that Quinn's new kit is more brain dead than it was before. People say that it feels lackluster and part of the reason for that is that the meaningful decisions are gone and have been replaced with something far easier and less satisfying.
To the heart of the matter: you asked how to get Riot to change the ult?
Truth is that Valor wasn't really the problem in this equation. It's Quinn. I feel as though Riot knows this but they don't want to give up the ranged part of Quinn for X reasons. But there's to much of a disconnect between the ranged super squishy nature and Quinn and the in your face Valor. Truth of the matter is that Quinn probably should have been a melee champion, and granted her the higher armor, health, and MR that fits more into the bruiser/melee assassin role.
http://img1.wikia.nocookie.net/__cb20140309225120/leagueoflegends/images/3/3b/Quinn_Concept_2.png
Her ult would be better off going back to what it was, and then actually changing Quinn to melee. It wouldn't fix all of her problems but it solves the core issue which was the disconnect. It's hilarious that she was part of the ADC rework because she was never really an ADC.
I could probably go on much further but that's really the heart of it.