Have you uploaded the task to the correct one launchd? Based on where you placed the file, it looks like you should be doing sudo launchctl load /Library/LaunchDaemons/com.dotcafe.DCDMySQLBackup.plist. Subsequently, can you sudo launchctl start com.dotcafe.DCDMySQLBackup?
launchd , , , , launchctl start . , , cron.