I checked out Syndra's win rate % by game length, it's not what I expected. For some reason I figured she'd get better as the game progresses, not the other way around. I think I might hold out on getting her, I don't really like playing against the clock
she's not playing against the clock, that's just dumb. like stone said, she's not pantheon
she's a lane bully and an assassin-like mage and both of those things have reduced relevancy late game so she just loses effectiveness as the game goes on. she still has pick potential and aoe and she can still oneshot carries and provide cc, so she's still good for most of the game
she's just not ori
The simplicity of her kit means that she can't be good without being too good.
Her skill ceiling is being able to use her passive as an auto attack reset.
not only that but her kit being able to affect from one to five champions at once with similar ease also makes her really difficult to balance
her ult really exemplifies this, to land sona's ult you have to time it, aim it and position yourself in a way that catches the most people. it takes skill to get a great ult off, which is why the spell is allowed to be so devastatingly good. and even if you use it on a single enemy it's still a really good spell. this is all thanks to her ult being easy to whiff and dependant on skill (both sona's and her enemies) and high cooldowns (not only ult but also flash).
the rest of her kit by comparison is just spammy and uninvolved. you press heal when someone's low, you press dmg when a baddie is close, you press speed whenever you want your passive lol. and with the same amount of effort it might hit one or all five of your teammates, and so it has to be balanced around that best possible scenario being as easy to access to as the worst, making all her spells feel like weak invisible power (even if they're really strong).
that's why they reduced the aura areas, to make best possible scenarios a bit more difficult to happen. but now she feels awful to play and she's still winning through invisible power.
so yeah, the auras concept, maybe that's just gotta go