It's running as an after rule since the time does not get set until someone is assigned to the alert

Ok so this should be a maintenance rule then?  I'm new to the event management module.  The business rule runs when the correlation _rule is 0 or 1 and the Assigned to field is not null and the state is not closed.

So should I just make this BR into a maintenance rule then?  How are maintenance rules run with the em_alerts?