Have you tried Outlook 2011 on the GM candidate? It's the first El Capitan I've installed and Outlook 2011 just hangs and dies for me.
Have not tried the GM - I am hoping they continue the El CAP beta and will wait and stay on the beta - version (15A278b) and outlook 14.5.5 (version 150821)
Outlook does crash once in a while - seems to happen when I boot up or restart. I never used to shut down my computer but since I upgraded to el cap it takes less than 14 seconds to start up, login and start outlook - that is "way cool".
I thought my outlook problems were gone but they still happen - less frequently - I have to say despite the crashes I have not lost one email - even long emails that I was ready to send and then the spinning wheel shows up and I force quit and restart outlook - everything is still there.
I think the crashes are related to the exchange account sync, because when I turn off the exchange account outlook does not seem to crash - as much.
Some times after starting up - I have to restart outlook a few times - but once it starts working it works for hours with out a crash.
I know that does not sound great - but it works for me - too many cool things I about El Cap to go back to Yosemite.
If not for exchange I would switch to Thunderbird - which I installed at the first install of el cap beta and it has worked flawlessly and still does for all my IMAP email accounts - just not the exchange Micrs$#Ft account.
I can't wait to get off the outlook bandwagon, but unfortunately apple mail is even worse.