I saw the greyed-out “Mass edit” button, but hadn’t worked out that I had to select multiple items (turn them blue) from the filtered list of hosts in order to be able to use that button to set values across multiple entries. Once I did, it worked as intended.

So this one was a decision to actually attempt to make Groups more useful.

While it seems like it’s removing features, it actually enhances them.

Groups in the past were things that any host could join at any given point in time. Why is this a problem? Imagine HostA in 5 groups. What group applied what pieces of it to the host? Did a group apply anything to a Host? It could yes, but if I have HostA in GroupA and GroupB. GroupB has ImageB assigned to it, and GroupA has ImageA assigned to it. If you update a group (open and hit save) it would modify All hosts in the group. But now you’re looking at different group you may get confused.

So Yes you can still mass edit hosts based on groups in 1.6, you just do it from the Host page. (You can filter the list to specific groups)

Groups are now additive in nature. You assign Snapins, Printers, etc… to a group. (You can still apply to hosts as well, but groups aren’t applying to each individual host anymore). If a host is in multiple groups, things that arent’ assigned to that host, but assigned to the groups will now be applied to the hosts.

https://docs.fogproject.org/en/latest/1.6/management/web/groups/

This helps break it down a bit more technical, but hopefully more representative of the feature set.