Cluster Group - Application resources in this group - Bad Idea.
By default, when you create a Server Cluster, the clustering software creates the default groups. These are the groups created:
a. Cluster Group
b. Cluster Disk 1 and so on for each shared disk which is accessible by cluster node.
I have seen in many books and Microsoft recommendation not to keep the application resources in default cluster group that is Cluster Group. The Cluster Group keeps the "Core Resources" in it. The Core Resources for a cluster are "Network Name" and "IP Address" for the cluster. Clients use or access cluster using these resources. A failure of application resources may bring the cluster down because Cluster Group is set to "Restart Group" if any resource fails in this group. This function brings all the resources down (including Core Resources) in the Cluster Group. Let's think for a minute, if Core Resources (Network Name and Virtual IP Address) are down, can client access the cluster? No, they can't because Core Resources are down means cluster is also down. If you happen to keep application resources in default cluster group or you have to keep the application resources in this group, then remove the check "Restart Group" on the group's property.
Next....How Quorum Resource works Internally.