Sona is the worst support in the game
Now that i have your attention. Let me explain my logic. I am talking about Sona as a support , not her ability to be a burst mage once you have picked up Lich Bane and Echo, simply what she offers to her team as a utility support. As Sona currently exists, she is a garbage support character. Her utility is basically worthless. Bonus damage from Q can't be used against structures, it can be used up against a minion. Even if you/your ally land it against an enemy champion it's next to no base bonus damage. Her heal has horrible base value for the first two ranks. It has extremely high costs, and a fairly high cooldown thus preventing multiple use without items to negate some of these issues. Her shield requires you to be basically right next to your ally which often means that you simply can't shield them or have to run towards the enemy champions to try and save your ally (often ending up in both of your deaths). Sona's bonus movement speed lasts for such a short period of time on her allies that it often requires multiple casts to see any tangible benefits. It is also the worst skill to rank up that currently exists in the game, with it's 1% bonus per rank and 2% bonus per rank in ultimate.
To make up for horrible base values, and poor utility, Sona is required to build heavy levels of AP and land multiple instances of her utility spells for them to have any bearing on team fights or in capturing objectives. Beyond these issues, Sona is also the only support champion (classified under the support role, not just a champion who CAN play support) who lacks a form of hard CC before level 6. While level 6 does offer Sona an AOE stun it also has a very long cooldown making it useless for simple trades/ applying non-all in pressure.
and
. Or did she get you there on the back of her insane item synergy with stuff like Lich Bane and Echo?
in that order.
2 Quints are used for CDR/lvl for the last 10% CDR
or 
to help my team kite
if they have tanks that I can help burn with the %hp burn
for extra movement speed and poke
against a heavy magic damage team