I use node specific alerts for more critical nodes etc., and group alerts for well, less worrisome ones. Here's what I use for the alert though and it works great. The custom property g_contacts must first not be empty, to avoid alerting on groups I don't need to worry about going down, warning etc.. This custom property is just a list of emails to notify.
Then the actual notification will include this variable (among many other things I typically include, node details url, alert details url, ack url):
It will give you a list of down, warning nodes in the group that caused the status change.