@aker
It's indeed AV-related ! Not clear to me why I didn't notice this during the first test I did earlier. When I disable AV before WSUSoffline is executing, it terminates within the same lapse of time as the pre-9.4 versions.
It's all related to the FOR-loop introduced in 9.4 and which seems to be needed due to the way MS is providing the information.
I'll have to remember to disable my AV every time I run WSUSoffline, because adding %TEMP% as an exception in my AV is a bridge to far. Just a pitty WSUSoffline isn't using an own subdir in %TEMP%. I certainly wouldn't mind to add that subdir as an exception in my AV.
Thanks !!
@WSUSUpdateAdmin
Could you please consider to use something like %TEMP%\WSUSOU instead of %TEMP%. That would be of a great help for those running into this problem.