Not sure if i fully understand your question, but this could be as simple as changing the URL you are providing.
Do you want the users to click a link and open automatically into the dashboard? as opposed to being sent into the Tableau interface in which they have to first pick the workbook?
If this is the case, you can change the url you provide the users, if they access it via url. If they use the application to access the workbooks, you can do an embedded view.
Could you elaborate on the issue?
You can get the user to click on "Make this my start page" in the top right of the screen.
In 8.2 that wouldn't take you right down to the view level but I think that might have been addressed in 8.3+
A note in addition to what Paul wrote: in order to set this up for other users, you'd have to log in as that user and use the "Make this my start page" option.
I agree that it would be nice to set the start page differently for different users, but there's nothing built into the product to allow for this from an admin perspective -- you might look into creating your own portal, or a set of links as described by Carlos. One user has shared how they've created their own custom landing page for Server users (in Tableau) here: Custom Tableau Server Landing Page | Tableau Support Communityh