I created a custom alarm and selected the event types "DasHostFailedEvent", no event substring, and the assigned severity is "Error." I assigned it to the top level and allowed propagation. I can see the event in vCenter but it's not triggering in Veeam reporter. I found that event type from http://www.veeam.com/support/vcEvents.html
so it seems like it should work but doesn't. I performed an init 6 from the cmd line on an ESX host for testing but no veeam event triggered.