My suggestion:
Fire/Fire Tanker
Sonic/Radiation Defender
Sonic/Radiation Defender
1. Lots of Area of Effect Damage.
2. The Radiation Blasts will lower Defense while the Sonic Primary lowers Damage Resistance.
3. stacked Resistance Shields are always a good thing
4.If both defenders take Heal other and Heal self as Pool Powers, the one drawback to Sonic Resonance goes away.
5. Lots of choices in power selection in case someone wants to avoid identical builds.
PS If you can find a Rad/Rad Defender as well, that would really sweeten the team.
Snoogins