Sona's Q aura isn't useful in it's current state
I've felt this way about it for quite a while now
This isn't really a matter of if Sona is underpowered or overpowered or not, I think she's actually pretty fine besides this one thing, but I'm sure many people can agree that a one time on-hit bonus that only works on auto-attacks isn't that useful and doesn't feel very impactful at all, especially during later into the game, and mages (or anyone who isn't reliant on auto-attacks for that matter) don't even get to make use of it
I usually only use Sona's Q for poke, the aura bonus is pretty irrelevant