Thanks for the detailed responses. I have thought about it a little more and realized that my two options of choice would either be:

4 affliction locks + holy/disc priest - Not having to face targets and dropping that many dots per target in a short amount of time looks like it could be killer. The AOE fears are nice, but many classes can counter it as well as diminishing returns. However, locks can stack stam pretty heavy and from what i've noticed in 5v5's on my lock...the locks are the tanks. An issue I also see are grounding totems as dots will not fire off on a target until the grounding is killed by direct damage.

5 shamans - Elemental shamans seem to dish out insane burst damage in the arena. 5 NS / Elem mastery chain lightnings would devastate a team of 5...especially if they are clumped together. 5 grounding totems also grants you immunity to any casters. I've seen some shamans hit upwards of 35-40% crit. Tied with 1.5 sec chain lightnings and an array of shocks...the combination seems deadly. I'd probably designate the main shaman resto for the extra mana tide totem/survivability. 4 elemental shamans should plow through 12k hp instantly.

So, I'll probably end up flipping a coin and seeing where it goes. Both groups seem pretty insane. Only issue I see with the shaman group is having to be facing the targets.

Right now I only have the hardware to support a group of 3. Not sure yet if I want to drop the money on another two machines/displays for a 5v5 setup.