I have the same group makeup and am thinking of two completely different approaches:
Approach 1:
1 - name my team : ONLY HERE FOR FREE EPICS KILL US QUICKLY AS WE HAVE BETTER THINGS TO DO
2 - enter arena
3 - /sleep

Approach 2:
1 - name my team : EPIC FAIL
2 - enter arena
3 - focus macros for silence,cs,cc - you may be able to keep a priest cs or silenced for ages - priceless
4 - DPS the rest starting with the lovely opening move: PoM Pyro asap
5 - go completely NUTS
6 - EPIC FAIL

remember: 3 mages =
3 Arc Blast
3 sheep
3 CoC
3 Frost Nova
3 Blast wave
3 Pyro
3 Improved Counterspell and you have a priest for silence as well
3 Invisibility

with targettaget macros for dps and using focustarget for CS/Silence/Sheep it could be not so bad.

I once played a 2x2 with another player against what I'm pretty sure was 2 multibox hunters. What they did was wait in the starting area for ages until we finally gave up and went looking for them, they nuked us. I'm thinking of using the same strategy, it was really unsettling.