for batch upload (including one using DDI) which we've built on and have used as part of a migration from Nesstar to Dataverse in the past. There are also a lot of existing scripts available for migrating from one Dataverse to another installation and this requires bulk uploads (see our's for example
The Dataverse API documentation is also pretty good
API Guide — Dataverse.org
In terms of batch metadata updates after upload and publishing, we do this directly in the database using the metadata tables but would love to see some kind of Database Admin Tool for batch edits to be made available. Sometimes we get a request to add a 'Series' field value to over 100 datasets, for example, or to add controlled vocabularies after publishing to enhance the dataset's discovery and reuse.