they offer very little else to the raid. If your group has a monk, the Dark Knight brings nothing to the table at all
Actually DRK is great in Savage A1 since the oppressor does magical damage, have the monk DPS as usual on the first one, then have the DRK off tank the first one and pick up the other so its able to use Delirium. Also the same with A3 if that is in fact magical aswell. DRK could very well be of great use to raid groups.