Delayed Alerting

Hi, 

Not sure if this is doable or not but I have set up an alert rule to track a collection of Network Devices and set an escalation chain with a single blank first entry and a distribution group as the second escalation point with as delay of 10 minutes. 

The problem I am having is alerts are being sent every 10 minutes for a device being down, I altered the alert rate to 1 every hour but then it just generated a single device down alert so if multiple were down it would only tell me about 1. 

Support advised to alter the ping module to collect status every hour for example but that's then a big gap in-between where something could be down without knowledge. 

Without setting up a single alert rule per device - not sure how to achieve the above, I thought about automated sdt if an alert is generated to stop the noise but doesn't look possible. 

Anyone ever had a requirement for anything like this or just purely unique (odd way) I am trying to do something?

Any advise or shut downs happy to hear :-)

Thanks, 

Simon