When we first loaded EBL records into voyager, we noticed that the EBL records seemed to dominate relevance ranked keyword search results. We contacted Exlibris to ask them if they knew anything that might account for this issue. Their reply was that same-relevance records are displayed in the order the search finds them - which tends to be newer records first.
In July 2014 we regenerated the voyager index and this seems to have resolved the relevance issue. We also began running a keyword index regeneration on a daily basis.