Average Count

Hi, without investigating much about the logics about the calculation of 'Employed' and 'CurrentEmps' i assume your DAX formula will result not in an incorrect answer but in an error due to the fact you put two RETURN statement inside one DAX formula. Before thinking about the quality of your calculation i would try to run this instead:

VAR CurrentEmps =
CALCULATE (
COUNTX (
FILTER (
STAFFMASTER,
STAFFMASTER[Current Employment: Start Date] <= MAX ( 'Date'[Date] )
&& (
ISBLANK ( staffmaster[End Date] )
|| staffmaster[End Date] > MAX ( 'Date'[Date] )
)
),
( STAFFMASTER[Unique Id] )
),
CROSSFILTER ( STAFFMASTER[Current Employment: Start Date], 'Date'[Date], NONE )
)
VAR Employed =
CALCULATE (
DISTINCTCOUNT ( 'STAFFMASTER'[Unique ID] ),
'STAFFMASTER'[Current Employment: Start Date] <= MIN ( 'Date'[Date] )
&& (
'STAFFMASTER'[End Date] >= MAX ( 'Date'[Date] )
|| ISBLANK ( 'STAFFMASTER'[End Date] )
),
CROSSFILTER ( 'Date'[Date], STAFFMASTER[Current Employment: Start Date], NONE )
)
RETURN
( CurrentEmps + Employed ) / 2

Logics are the same as yours but in my opinion minD and maxD variables were not necessary.

Hope this will help you! Cheers!