Can you try setting the dashboard size to Automatic? This may be a better way to go to avoid screen resolution issues. Here's the link with more info: http://onlinehelp.tableau.com/current/pro/online/en-us/help.htm#dashboards_organize_size.html
the IPad Pro resolution is hidden (wrongly) under "device type: Desktop / iPad Pro 1366x1024"
I know... it's confusing at best.