This should work if you have a bit of lag ie if they dont change target too fast, then all 3 droods should cast on the otherones target. Of course once cast the targets have now swapped. You'll have to manually target 3 seperate targets before hand though.

then u can just spam the cyclone button.

drooda
/cast [target=droodb-target] cyclone

droodb
/cast [target=droodc-target] cyclone

droodc
/cast [target=drooda-target] cyclone