ive cleared it 2 ways....

1st - stick to a corner killing the arm the spawns at the top to prevent the tank gettin stunned n thrown then spread out when u see him casting the tornado thingie

2nd - have a dps eithier side with healer staying around the middle killing the middle arm so healer dont get stunned easier this way to prevent 2-3 tornados spawning on same spot

dont know if its supposed to be done those ways but we have cleared it doin those methods but didnt seem to take to long for us xD