I prefer to declare myself a Quinn _(and Valor)_ main
Playing her since the middle of S4, I've found her kit to be interesting, ect.. ect..
She was an okay champion who struggled because of bugs that were mostly fixed with her rework.
But you don't care about that, you care about the new supersonic Quinn wrecking your entire team.
So the only thing riot needs to do to fix Quinn?
Lower Harrier's damage.
Harrier does too much damage, and they never thought to look at how that damage might escalate when letting her Q mark a target.
A single harrier AA can do upwards of **1600 damage**.
It's too much. Just lower the scalings (But don't make her passive useless please), and you can fix the majority of Quinn's problems without completely reworking her.