So after she does her ultimate and destroys the pillars? She will make a purple tornado with a clear area in the middle. The Tank should take her to the top end and the Healer stands at the opposite end so they are not in range of her AoE. She will spawn some adds that need to be nuked down, She'll teleport to the middle after a while and do an attack you need to get behind her for this. She does another attack where she teleports to one side of the tornado so stand at the other end. The attack takes up one half of the tornado and it's instant death.

She'll do adds again and just repeat the phase though she should be dead by the time the next adds are downed. As long as people don't derp into stuff that purple tornado phase is pretty easy.