To keep this thread busy and to document how strong pain is but how people try to find work arounds for a major disconnect of the the two largest software eco systems, here is another idea I tried w/o success so far unfortunately.
I once had Owncloud on a Raspberry PI on my DSL router @home to sync Contacts and Calendar via the tool:
http://www.bynari.net/product/bynari-webdav-collaborator/
It worked so far so good, but was not 100% reliable/compatible, basically because the Ownclouds performance on the Raspberry was quite weak.
Thats why I decided to move to iCloud, which worked perfectly until Office 2016😠
I just gave the Outlook pluging from Bynari another try, but it was unable to discover the iclouds CalDav/CarDav servers at contacts.icloud.com and caldav.icloud.com. If anyone has time to play and finds how to get this work, it could become a real attractive interim solution.