First off, thanks for testing this and throwing some results out there. I thought Boomkins were a possibility, and I might have to test this myself, but thanks for sharing your results, pretty much confirming my beliefs.

I'm afraid the sad fact is that all the other ranged classes require some sort of "skill" to stay alive in an arena enviroment, (kites, fears, frost novas, roots, traps, cyclones, ice blocks, feign deaths and so on and so forth), where as the Shaman have it pretty passively (Grounding totem, Shields and Mail armor). I can't see four of those micro intensive classes doing well unless you spend A LOT (emphasis on LOT) of time practicing, and even then you'd have to be madly skilled to pull it off.
Add to that the fact that Shamans have the better burst damage, with possible exception of POM mages, and I think it's pretty clear why Shamans are the "easier" and better choice. They just function better with less of a brain and micro devoted to each.
To put it in another way, with a group of Shaman you can use nearly all their abilities to full potential. With a group of Mages/Warlocks/Whatever, you really can't. Individually, the Shaman is weaker than any of the others, but once you strip the micro from the classes, as you do when multiboxing, Shamans still have most of their abilities, either passively, or to be plopped down in form of totems affecting the whole group. The other classes have more individual skills, and without them they are left fairly defenseless.

I've given this a fair bit of thought myself, because I'm thinking along the same lines you are. With Multiboxing becoming more popular, I don't want to be "Just another noob shaman group". I'd want to be different. But in Arenas, I don't think you have a lot of choice, sadly...
Maybe 4-5 Shadow Priests? Their passive healing might offset some of the incoming damage. But then, I doubt this is viable.

Frost Mages. If the other team is clumped together as they usually, are, you could do some Water Elemental ranged freezing with FB's and lances, Frost Nova and four CoC... Bind Ice Block to four keys next to each other somewhere. It could work. Less burst damage, and less survivability, I think, but sheeps might tip the scales. Meh, I'm just speculating here.


I'd really love to hear it if someone thinks I'm wrong on this, by the way. I seriously do. Throw your thoughts in there ;)