Can't get Path exclusion to work in REST or Query Transform

I'm using SharePoint 2013 (on-premise) and can't seem to exclude certain back-end lists from search results.

I'm testing with "/Lists/WorkflowHistory/" and will add other lists later but I can't get this to work no matter what I do. I've tried

I've tried using the path exclusion in the Result Source > Query Transform:

{?{searchTerms} -path:"/Lists/WorkflowHistory/" -ContentClass=urn:content-class:SPSPeople} {?{searchTerms} -ContentClass=urn:content-class:SPSPeople} -path:"/Lists/WorkflowHistory/"

I've tried testing using REST (/_api/search/query?) with the following: http://ift.tt/1CxmI6z

http://ift.tt/1D0O2Ir

http://ift.tt/1D0O2It

I even tried to exclude the PATH starting with the domain http://ift.tt/1CxmFHX

But I'm still getting the WorkFlowHistory folders.

What am I missing? Any suggestions how to get this to work?