It is my experience that "dot releases" (such as 11.3.x) were possible without having to shut down all the primary servers. When trying to roll-out 11.3.1, however, it is telling me it can't schedule because:

"Unable to complete your request for the following reason: The ZENworks Server or the ZENworks Loader services are running on one or more Primary Servers. Shut down the services before proceeding."

Was this a change made in SP3? I have updated to almost every release of ZENworks and only had to shutdown all Primaries during an SP or Major Version upgrade.