Are you using Polygons (or Filled Maps) on your vizes?
What happens if you would render geo-Marks as Dots?
To test, please make a copy of your map viz using Circles as the Mark Type.
Publish it to your TS and test side-by-side with your original 'slow map' viz.
Could you see any difference in render timings?
Thank you for responding Yuri. We actually display dots already to try to optimize the view.
I timed the response of simply displaying the generic Havana map which displays in about 1 second. The frustrating thing is with the exact same setup I don't see these issues at other customers. I will keep your test in mind as I look for bottlenecks on the server itself. Something is bogging it down but at least with the havana test I believe I should rule out the forward proxy & network. When I find the issue I'll respond.
Problem #1, we we're using the default 'Run As User'. This doesn't allow Tableau Server to optimally perform.
We also set vizqlserver.browser.render to false (more about this here) and force the server to handle all rendering. A double edge sword to performance but as some servers may not have an internet connection the map could occasionally not render but this would insure it always would; barring some other work around which we didn't want to entertain.
This took care of almost all of our issues. From here we went into fine tuning of dashboards; removed polygon shading (there was one that did that), etc.