Nick:
.. that way anyone that needs multiple files can hold off downloading them until all the "dump_run" fields match up, so as to more easily avoid problems of mixing files from different dumps. (It's true that this field can currently be pulled from the directory in the <url> field, but if a different field is used then the url can point just about anywhere, such as potentially using different hostnames for different dumps, or changing directory structure.)
Not for the /latest What about making the -latest- files an http redirect to the real ones instead of symlinks? You can grab -latest-file swith the correct names, you know the date... The only possible problem i see are broken utilities to download the wiki which doesn't properly handle the full http. However, as there is no system which uses them, i don't think it to be very used.
About the meaning of 'latest', we could split in latestfile / latestcomplete with both senses.