Typically a SCD type 2 has those validFrom and validTo fields in the dimension table. You can create your DSV by filtering on only those that have the validTo be NULL. These are necessary for this type of reporting. Of course changing the table is not enough even if you could. You would likely need to alter the actual process that populates the database to use those new fields as well.

In you situation I am assuming your distinct count is 1000 but the individual sums total 1500 (using my example)? Are you using your own keys or the operation systems ID? Is there some inconsistency/error with the key values for the lines in the dimension table?