How to handle event storms

Rather simple explanation: Based on your question I can assume your unmanaging devices, rather than muting devices.  When you unmanage a device it's breaks the parent/child relationship, which in turn causes the children to alarm when the parent goes off-line.  If you have a newer Orion version that has the 'mute' function use that instead of the unmange. 

Mute retains the parent/child relationship, it's easier to manage if you have multiple children and it doesn't affect SLA's as much as unmanage does.

Check out 'manage dependencies'  option for parent child co-relationship, create a dependency as required to suppress the alerts generated from children beneath it (note: you will need to define this yourself)

Settings -> All Settings -> Manage Dependencies

Thank you- managed dependencies seems to be the option to explore. I'll update with results. Thank you!