Back in TBC (When I still did Arena :P ) I fought a 5x mage set up once, me playing 4x shaman + individual healer

Out of ALL the arena I ever did. That was by far the most hectic fight ever. I actually won. Grounding totems and waiting them out, nuking one down before they had a chance to start. But even then it was just wicked. The actual heat of the fight literally only lasted like 4-5 seconds, and like 7 people were dead in that time. (Two of me, four of them. It then lasted for a while longer as their last mage started to kite. :P )

I think, mages vs shaman boxer. It's all down to who gets off the start. Refreshing grounding totems won't matter. As the fight will be decided before groundings can be refreshed. If the mage boxer waits until the moment the shaman boxers drops groundings, then proceeds to blink in, get rid of totems. It would seriously be a close call. Imo. But a second off, and the tide would be turned.

Most fun fight I ever did. :P