My vote is very specific. I would vote for a Sonic/Sonic Defender. They are rare, one of the most rare builds you will find being actively played everyday. Like another post above said, the people who usually play these sets often are mature and experienced and know what they are doing. The debuff are DEVASTATING, take a look at this--
Sonic/ primary on a Defender, Sonic Siphoon is a -30% resistance debuff, disruption field toggle (to boot!) is a -30% resistance debuff as well PbAoE on targe ally. That's a very nice -60% resistance debuff.
31 resist buff on teammates on all dmg except psy and an additional 21% resist buff on teammates, a very significant resistance buff of 51% to your teammates from dmg. Tell a shield brute with a Sonic/ Defender that his numbers are better, overall, than a decked out invul/ tanker. Then you have a mez protect in the Dispersion field and CLARITY is just the equivalent of clear mind from empths. That is just fantastic.
In STFs or Khan or other similar circumstances, they can and will cage other AVs, when you are concentrating on one and do not want the other AVs to bother or hinder what you are doing. Depending on their recharge, they can cage two for your team, kill one AV then move on.
Speaking of the /Sonic secondary, the attacks from a Defender do -20% resist debuff. Taking an opponent to more than -100% resistance debuff in seconds is just SWEETNESS.
The only bad thing I see with Sonic/Sonic Defenders is they are just as rare as purple recipe drops. I am inclined to think I get more purple drops than I get to see Sonic/Sonic Defenders.
Having just come from another thread my vote/s would go to Sonic Resonance and Kinetics, both have their pros and cons but if both were on the same team then things are gonna get steamrolled.