The root cause took quite a long time to diagnose, and we worked very closely with Apple to track it down.
We're well aware of the hang problem in Office 2011 and are working on a fix. Microsoft for the Big Loss on Outlook and Mac OS 10.11. No one at Microsoft testing 2011 on Mac OS 10.11? WTH?! The problem with that last option is they arbitrarily removed support for Exchange 2007 from Outlook 2016 so that's not an option.
Microsoft has a KB article where they recommend either not updating from Yosemite or to upgrade Outlook to 2016. Earlier it would just hang with a beach ball so I closed it and then when I reopened it a few hours later it is working for now. Outlook 2011 is having some major issues with El Capitan too.