First, as said, play what you like. Second, tank, 3 dps and a healer is a good strategy. Only advice I'd offer is some variety in buffs and armor types.
My biggest complaint with the standard pally + 4 shaman team was farming item upgrades. Needing 4 semi-rare drops for the casters was a huge time-sink.
2 mages, druid, and a shaman would let you use any caster drop.
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