What we do on this fight, is the following.
Nature: 4 DPS; 1 Tank; 1 Healer.
Wind: 2 DPS; 1 Healer
Frost: 1 Tank; 1 Healer
At the 2nd ultimate, the DPS at Wind moves pretty early to Frost platform (as they cant do more damage to Wind anyways).
When the 2nd Ultimate finishes all dps, a tank and a healer moves to Nature platform and kills him.
All move back to Frost, while one DPS continues to finish of the Wind platform.
Profit