MDG is not complete solution for data quality. It's main strength is Governance during creation/change of data records. It has limited support for data consolidation/cleansing for mass data.
For Data quality specialised products in SAP portfolio are SAP BOIS and SAP BODS.
SAP BOIS -> Define business rules based cleansing packages, Measure data quality metrics based on these.
SAP BODS -> Consolidate data from different systems, Cleanse , standardize , De-duplicate, Enrichment of data using address directories, migration of cleansed data to MDG hub.