Hey I have run a few games with ALL flat AP's and 9-0-21 masteries on Sona and Zyra and done well. That said, while I am a good player and a support main it probably had a more to do with the fact that the enemy team just weren't good. ;D
I think the problem is people want to treat Sona like they did in S2/3 and while she can be a bully it's way too easy to punish her for it now. I prefer to pick her into lanes where we need to just sustain and if we have the option to be aggressive I can pop my q for some bonus dmg. I have driven a few teams insane by having my ADC go completely passive and just farm and safe poke while they are going hard trying to make plays.