After cloning a policy you will notice that severities do not work until a policy is resaved.
16RU2
This is happening due to a processing-order header not being formatted properly.
Working example from an xml export:
<processing-order>-2147483648</processing-order>
Not working example:
<processing-order xsi:nil="true" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
Notice the not working example the processing-order header is incorrect.
Workaround:
Make a minor edit and resave the policy.
Fix:
Upgrade to 16.1