I don't think there is such a thing as a dead group...as long as people can join a group there is the potential for it to be active.

Also I've noticed that groups have cycles. Some will be really active for several months and then activity will fall off again, until something else picks up again. Others plod steadily along, with a post here and there, but that doesn't mean that they are dead.

I think it is up to those who join a group to get their sesterces worth out of it. Scribes and demis can help, but as far as I know, unless a scribe is in an administrative position within a group, they cannot promote anyone to a higher level in a group that they are not already a member of.