A quick solution would be the use of a Gateway plugin called "Gateway-severityCount", where it would display the number of severities per category, i.e. how many critical items are in reported by a particular Netprobe, Managed Entity, etc.
From the below example, I have defined attributes via Managed entities to distinguish one entity to the other, i.e. OS type, Application purpose, etc;
Then, in my sampler configuration, I defined the View path to display the assigned Attributes
Which yielded the following data view
For more information, check out the documentation on the Severity Count plugin.