Thanks for the sample. The upcoming release of dcm2niix does convert your 2D mosaic to a 3D volume.
  https://github.com/rordenlab/dcm2niix/releases
However, there is a serious issue with your image. Specifically, the CSAImageHeaderInfo (0029,1010) has been stripped. It should contain rich data about your sequence
http://nipy.org/nibabel/dicom/siemens_cs...
but has been removed.
While the latest releases of my software is able to detect that this is a mosaic using NumberOfImagesInMosaic (0019,100A), many of the parameters of this image have been removed, so no software will be able to work out phase encoding direction, effective echo spacing, etc. I suggest go directly to your scanner to get the raw data. You should also look carefully at the providence of your data and identify the tool that has stripped out this vital information. The last tool to save the DICOM data (and therefore the prime suspect) is:
MAROTECH REGISTER 5.0