Well, you could use custom properties, or I have instituted a naming standard on devices (with Location) and alerts are setup for those locations.
Basically the same as jbaulsir's response, I use a custom property called 'DeviceClass'.
And my advanced alerts look like
Trigger alert when all of the following apply
- Node status is equal to down
- DeviceClass is equal to core
And so on for all the different groups of devices.