Sorry to hear that this isn't working for you. We use SQL Server a lot around here, and don't have a lot of issues. Can you say a bit more about the symptoms you're seeing? Is there an error, or is the system just spinning -- or something else?
I spoke to a Tableau support person and it appears that I need an upgrade of memory on my office PC.
My PC only has 8 GB of ram and I'm having it upgraded to 16 GB. I'm hopping this fixes the issue.