It should already do that actually. Unless you have "Top only" switched on in Config Switches.
As soon as ServerA has tried all articles, ServerB takes over and ServerA goes on to the next one. At least that is what I see in the tests.
Simultaneous Downloads
Re: Simultaneous Downloads
If you like our support, check our special newsserver deal or donate at: https://sabnzbd.org/donate
Re: Simultaneous Downloads
Normally it should. I might have to test it again.
If you like our support, check our special newsserver deal or donate at: https://sabnzbd.org/donate