The solr.xml I posted was initially just copy-and-pasted from some site that documented it (which also suggested that these values not be altered). The only values we have changed are coreRootDirectory, host, zkHost and (I think) zkClientTimeout.
We don't use transient cores so the value isn't terribly relevant to us. In fact, we use configuration management systems to manage core directories and core.properties files in a totally different location separate from solr.home and solr.xml. The only reason this (the problem discussed in this ticket) is an issue for us is because it makes it impossible to perform dynamic shardsplitting as the user we run Solr as doesn't have write access to solr.home.