Conquest of the artefact camp

Is it okay if some of the fighters belonging to Don's camp die? Are they needed for any quests after this current quest? Thanks.

For some early quests, you need them. In fact in one set of quests you may end up killing some members of the Order, which will slightly affect later quests for them. Mind you, at one point I wiped out most of the camp and the Don still spoke to me!!