So I've pulled the Sona changes for now as we don't want to ship them for 6.10. They're likely to come back however for a future patch
Thank you so much for your testing and feedback.
Things I learned.
* Aura size is important. We could likely get away with a small size decrease to trim power, but there's a line that can be crossed at which point the auras become too small and feel unusable.
* Q is Sona's primary laning tool and giving it a crazy long CD early makes for a pretty sad laning phase. Like aura sizes, early CD on Q can likely stand a minor nerf but make it too high and Sona starts feeling like she doesn't have anything to do.
* E having a higher selfish MS buff is likely good overall for making Sona feel like a more impactful character, especially when most of the rest of her power is in her harder to feel auras. I think opening up Sona's pattern to try things like dodging skill shots, escaping ganks, and chasing/engaging without flash will overall in the long run make her more satisfying and easier to balance.
* Need to be careful about changes that would allow Sona to get too tanky, especially in a world where she can move a lot faster. Probably good that she's able to be jumped on and killed when her E and R are down.