The darkness certainly makes things interesting, and there is a certain oppressing feeling about it all - a nice thing to change the atmosphere of the game somewhat.
But unfortunately, I (together with my friends) didn’t find this one quite as fun as Tzeentchian Twins. While staying together around the torch changes gameplay significantly enough, I felt it was too restrictive and ended up tedious. It also discourages any kind of exploration: Even the usual Grimoires and Tomes need to be fetched together, and you certainly cannot (effectively) go search for the art pieces. I think it might also feel too similar a restriction to the (showcased in the dev Stream) Mutator that forces us to stay together or take damage. After all, with only one torch, we’re effectively bound to a single small area anyway.
I think that adding one more torch, so that we could (occasionally) actually split up, or someone could take a quick peek in a corner, could actually ease up at least some of these. It would also allow a bit larger effective battle area even when the torches are tossed down to fight. I’ve seen some people asking for a torch for everyone, but I think that’d be overkill, and would take away a lot of the special challenge anyway.