I have read this issue now a couple of time, I have the same issue.
After upgrade to Yosemite I can not open the documents from Sharepoint any more. None of the procedures work. I have tried, Safari, Chrome, Document Connection, opening the link in one of the office apps. It all fails. The only option I have is downloading to my disk and edit it then and then upload it again.
When I upgraded to Yosemite, I did a clean install and then a new install for Office 2011. I have also reinstalled it, nothing works.
I really hope this can be solved