^^ This. Keep them on follow and keep the tank close to the group. Sheep always broke before he teleported for me. Once he teleports start running to the other side of the pillar. Get lined up and start casting a group heal for the shadow bolt spam. Repeat the above and run back and forth along the same pillar. The most important key to survival is running as soon as he teleports. If you do that you will have plenty of time to get lined up and heal.