I've done 12 tables as a join from Access in Tableau and it works fine, however it was only returning 29k rows (source tables had millions of records). I'm wondering about your statements that there are "about 100k rows total for all tabs" with "these tables need to have only one connection point but in reality the table names are one-to-many". Does that mean that you'd expect to be returning 100k rows? If so, and the loader is getting into the millions, then something in your join is off. In that case, would you be better off with a series of queries that get UNION'ed together into one big query that is entered as Custom SQL for the Tableau connection?