use Core.deleteAsync() instead. This new version does not allow passing an identifier but only objects, however within this deprecated method the object is simply retrieved using Core.retrieveId() as well. To make this perform better, you should gather ids and retrieve all objects with Core.retrieveIdList() and then use Core.deleteAsync using the list.
Member com.mendix.core.Core.removeBatch (IContext context, String objectType, int batchSize, boolean autoCommit, boolean useDeleteBehavior)
This is no longer needed for performance, use Core.deleteWithoutEvents.