Tom,
On the Occitan Wikipedia they indicate the VIAF (and other) identifiers are shown from Wikidata. When a new identifier is added, this new identifier will be shown as well. When it is changed it is changed as well.
When information in both Wikidata and Wikipedia is the same, it would be good when the information is removed from Wikipedia (and shown from Wikidata). When there is a difference, the information needs to be verified and the resolution needs to go to Wikidata and sourced. In this way information will gradually become be improved and be available in more Wikipedias.
Yes you can concentrate your efforts on Wikipedia but it will only benefit one Wikipedia. It could do so much more good.
Thanks,
GerardM