A question about Sona's strengths

recently I had a discussion involving what is good or bad about Sona

statistically, even at full build her damage is rather average, but its consistency is not given that it is all targeted

People discussing can not seem to wrap their heads around what really makes sona strong or not, so I wanted to bring up something of my own

Some people claim that sona's ability to debuff her opponents reliably is her strength.

Others claim that it's her ability to buff and debuff at the same time without reference to her offensive abilities.

with how the current meta is centered, I wanted to discuss Sona's benefit to auto attackers or anyone who can get in range to auto attack. Her Q aura. at max level, her Q aura applies 30 + 30% AP to anyone tagged on their next auto attack.

Does this effect refresh if the ally is within sona's aura or is it a once-only effect?

Although that is an important question, I would also like to bring up the effectiveness of her Q aura when it gets spread out. Even when only applied once, it can add a potential of 120 + 120% AP bonus damage spread around her team that can be reapplied at max 4.8 seconds, min 2.65 seconds

#So, Sona players, in your experience, can you answer these claims?