Help needed with filtering

Ok so I have a problem that I think means I've missed something really obvious and simple but I can't see what.  I have three tables:

Data table:

Client Name, Employee ID, Task Name, Duration, Date of Service

Staff table:

Staff Name, Employee ID, Staff Level

Role table:

Task Name, Role Name

Staff Name is connected to Data table through the Employee ID, Role Table is connect to Data table through Task Name.

I can do a visual showing the number of hours per Role based on the data table.  What I want to do is a visual showing how many employees have undertaken the different Role types by staff level.  I thought that having the three tables connected the way I do it should be a simple case of showing the roles, staff level and then doing a distinct count of the employee codes.  But when I do all the answers come up with the total number of staff, see below.  Obviously I'm missing a step here with mapping the relationship or something but I can't figure out how else to filter this.

Any help would be appreciated.  Thanks,