The Google Scholar (Darcy Darpa) team provided the following recommendations to our repository team in the summer of 2015. Looking at these recommendations, I believe that these recommendations apply to all DSpace instances, not just to our repository.
1) It would be good if you could change "citation_date" to "citation_publication_date".
(2) For dissertations/theses, please change "citation_publisher" to "citation_dissertation_institution".
(3) The author name is best understood by the Scholar indexing system if it is "Firstname Middlename Surname".
(4) The "citation_abstract_html_url" tag and value are not needed.
(5) If a full-text PDF for one of your papers/theses/disserations is available for indexing, please include that URL in a "citation_pdf_url" metatag. This is a key tag and value that enables the Scholar indexing system to associate the authoritative bibliographic metadata in the landing page/record with the actual document.
Based on this set of recommendations, I believe that #1 and #4 could be addressed with a code fix. I think #2 and #5 are already in place. #3 is a data issue rather than a code issue.