Delta update takes hours to complete. Various targets were individually taking about a minute to update.
ITMS 7.6 - 8.1
A new target was being created for each patch policy. In addition to all of the extra targets instead of reusing a single target, the filter that the targets were based on had extra includes and excludes that added an extra 10 seconds to the update but didn't affect the membership.
Attached (internally) is a SQL query that would update all of the references to the old slow targets (based on the original incorrect filter) to point to the single reusable correct target.
Please contact Symantec Support to obtain the script as it needs to be adjusted for your environment.