Importing the XML is 'the way to go'. I just tested with the following XML file, and that works fine in my ClearPass 6.7:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<TipsContents xmlns="http://www.avendasys.com/tipsapiDefs/1.0">
<TipsHeader exportTime="Thu Jan 25 09:57:28 CET 2018" version="6.7"/>
<LocalUsers>
<LocalUser changePwdNextLogin="false" enabled="true" roleName="[Employee]" passwordNtlmHash="" passwordHash="" password="testing123" userName="Local User import-test" userId="import01"/>
</LocalUsers>
</TipsContents>
What I did was export all accounts, remove the role-mapping section, changed password, username, userid. File was named LocalUser.xml.