Add a new enemy faction comprised entirely of evil Lightbearers! The Cult the Shadows of Yor could fill this role. Instead of them having their own adds. You could just make the adds another enemy faction caught in our crossfire. They could be sheilded Orange and Yellow health bars depending on how powerful they've grown and to kill them we would have to shoot their ghost or they'd come back in a few moments at full health. I think it could give us some interesting boss fights and Strikes. And it would be interesting to see our Ghosts reaction to some one abusing their light.