I running a mixed PVP team for arena.
I'm currently at 1395 rating and doing OK, will see how it works when I get better gear.
Feels like I'm nuking down teams with equal gear.

I 5 box, my team is:
Holy Pala
Bal Druid
Frost Mage
Ele Shaman
Surv Hunter - he is doing a lot of magic dmg so he benifits from Earth and Moon. As you said the most important thing is that he has aimed shot.

I rly like my setup. Dont know what classes I would get instead.
Maybe get a destuction warlock instead of the mage.