Bill, By sync, I assume you mean publishing? I have never had any performance issue with publishing and have published thousands of times. And at most it has only taken me a minute to publish anything. Sorry I know it is not much help other than to clue you in that this should not be an issue.
By sync, I mean syncing (ie updating the source file) of a Tableau Online (server based) file through my desktop using the desktop sync program. I am simply updating the file which already exists online with new daily data.