We did it with 2 tank, 3 healers, and 5 dps with each dps taking the shard for 9 stacks, have one healer on tanks for the first shard, other two healers on torments spamming heals, over heals will still grant stacks, we also bloodlust on the first crystal. after that crystal is done, those two healers are the tank healers and the other heals torment. they than go into their healer rotation on torments switching every crystal. it's tough to meet the dps requirement this method, but doable.