Extremely poor Report Manager publishing performance in R12.1.2

We have Oracle 12.1.2 and now use Report Manager in place of desktop ADI.  We are predominantly on Excel 2010 with a smaller number of users on 2007.  We are finding that the publisihng part of RM to is extremely poor for both versions of Excel.  With a content set containing only 25 cost centres Excel 2010 takes 8 minutes to publis and Excel 2007 takes 7 minutes.  During this time we have alos seen Outlook freeze until the report is published. 

Oracle's current response from development after escalating to Vice President level is;

"While they do understand the severity of this bug , they found they are running into certain design considerations that limit further performance upside. They are unlikely to be in a position to offer a solution in the short term. Therefore, in the meantime, in order to help get better performance, they plan to put in place a medium term project to evaluate a redesign of this area to achieve significant performance gains. However, at the moment, I do not have any details about the timeline for achieving this"