Currently the NumericRastrizer always gives a constant string "NumericRasterizer" to the resulting feature as "fme_basename", even if you set "fme_basename" to the "Group By" parameter. It would be better if the transformer could propagate "fme_basename" value of the input feature when the user set "fme_basename" to "Group By".
In addition, the transformer doesn't recognize attribute names which are set to the "Group By" parameter if the names contain Japanese characters and "Input is Ordered by Group" is set to "Yes". This also should be improved.