Hi @Julien1,
Welcome to the eazyBI community 
!
Which level objects are referenced in the Jira issues? Please share a screenshot of the Assets structure. Is each level a separate object type?
In a structure with fewer levels, you can rely on the Object dimension filtered by a specific type and its attribute dimensions. For example, to see the number of objects and issues created by each Person and their Department (attribute in Person type objects), I use the Object dimension “Person” type objects and the Person Department dimensions:
Complex calculations may be required for multi-level hierarchies, relying on inbound references. Please see these two community posts for more details - Assets: Object filtering by a similar attribute and Assets: How to Import "Inbound References" in eazyBI.
Best,
Roberts // support@eazybi.com