xmltotxt.sh

#!/bin/bash

if [ -z $1 ]
  then
        echo 'Sitemap must be provided as first argument.';exit 2
fi

# Helper function to read xml
read_dom () {
    local IFS=\>
    read -d \< ENTITY CONTENT
}

mkdir tmp
cd tmp
wget $1
cd ../

while read_dom; do
    if [[ $ENTITY = "loc" ]]; then
        echo $CONTENT
    fi
done < tmp/sitemap.xml > sitemap.txt

rm -rf tmp

Run this:

./xmltotxt.sh http://domain.com/path/to/sitemap.xml

Now you can siege all the urls:

siege -c50 -d10 -i -f sitemap.txt