I have used the "Bulk Send" feature in DocuSign which is very similar to a mail merge operation, but I am not aware of a methodology to use Outlook to create a mail merge and send through DocuSign. With "Bulk Send" there are a variety of options from single to multiple Recipients depending on how the CSV is configured. When a "Bulk Send" is used then envelopes are created for each CSV row and envelopes can be managed via the DocuSign Sent folder.

Thank you for the quick answer @David Schmitz​!

Can you add individualized letters and custom signing orders for each letter needing signature with DocuSign's bulk send feature? 

Unfortunately, the "bulk send" does not allow for too much variety. The "bulk send" must use the same document, so individualized letters is not something it supports. Also the "bulk send" is using a Template which has a set workflow structure and hence each envelope that is sent using that Template is using the same workflow.

Let me clarify what I mean by individualized letters. Lets say you have two documents, the first document is just a form that needs to be filled out, but the second document is specific information pertaining to that Recipient such as Name, perhaps Address, City, State, Zip, hair color. The second document could use data from the CSV to individualize the data in the second document to that Recipient. However if the second document actually contains text in the document that is specific to each Recipient (not using DocuSign fields to populate data) then this is not supported under "Bulk Send"