rather than worrying about their application class, just create a new group, with members of the "windows server" entity type, and pick the servers you want. create a notification subscription that alerts the appropriate users on this new group and uses all classes. i believe "windows server" contains *everything* that goes on on a given server.
i had the opposite problem, where i was using "windows server" as group members, but the people i was notifying didn't care to know about SQL or IIS errors, just operating system and hardware errors.