The problem with Sona's Q is the same as the problem with Fiora's W

One autoattack doesn't make a difference.

ADC damage comes from MULTIPLE autoattacks. Buffing just the one makes it too easy to misclick, or to miss out due to the short buff duration.

With Fiora at least you can time it to parry a modified auto (like Rengar's Savagery), or to parry the attack that would have killed you. Sona just has to blindly bubble the ADC and hope for the best.

To restore the flavor and intent of the original Hymn of Valor - defined here as a consistent increase in offensive power for all allies within range - Sona's new Q needs to proc more than once, either proccing constantly over the buff's duration or being able to be applied to a given champion multiple times.

Yeah, how about that idea? If your ally consumes the buff, you can reapply it by keeping them within the bubble. Reward for risk.

And while we're at it, how about letting champions apply the buff with spell damage, too? It works okay for the Spellthief line.