One at a time there buckaroo
Dynamic Queries into group membership seem to update at least as often as the polling cycle - all my groups are query based and no issue yet.
As for report on who is lonely - paste this into a Custom SQL report then add using the Report from Report Writer resource to your page of choice
select region,sitecode,nodeid,Caption,contact
from nodes
where
not Caption in (
SELECT distinct [FullName]
FROM [ContainerMemberSnapshots]
where [EntityDisplayName] = 'Node'
)