eazyBI automatically sums up data in a hierarchy. Therefore, measure Hours spent for Story in sub-task hierarchy will work similarly like Hours spent with sub-tasks.
If you would like to see hours spent per each issue without summing it up, you can define a new measure using a tuple with issue type of the issue:
([Measures].[Hours spent],
[Issue Type].[Issue type].GetmemberByKey(
[Issue].CurrentHierarchyMember.Get("Issue type ID")
))