Can't share the trace as it's 1.25GB and 128MB compressed. One thing I did notice is that it's disabling (rather saving) some as I can see 776 users changed (pxcommitdatetime) during the run but there are 1187 in total.
What I don't understand is why it's selecting every user within this time period. Surely it should only be selecting users that are not yet disabled, which would reduce the list significantly 178.
I've just done a private edit on pzDisableDormantOperators and changed the Obj-Browse selection to only include none disabled operators.
This run has removed the remaining dormant operators. So this suggests there is an issue with the OOTB activity when there are lots of users.
Having looked at last nights run in production and checking the database, I can see that only 749 users were (saved) disabled out of 2431 which incidently happens to match the maxUserCount in the activity.