Meta Query Sorting with relation => OR not behaving as expected

[tcaneeaglepub]

When sorting on multiple meta query clauses with the default AND relation the sorting works as expected. When sorting with an OR relation the sorting does not function as expected.

'meta_query' => array(
	//'relation' => 'OR',// when turning this on the sorting does not work..
	'cornerstone_clause' => array(
		'key' => '_yst_is_cornerstone',
		'compare' => 'EXISTS',
		'type' => 'BINARY',
	),
	'count_clause' => array(
		'key' => 'erp_post_views_count',
		'compare' => '>',
		'value' => 0,
		'type' => 'NUMERIC',
	),
),
'orderby' => array(
	'cornerstone_clause' => 'DESC',
	'count_clause' => 'DESC',
),

The idea of the query is to first show any posts that contain '_yst_is_cornerstone' and sort the remaining by 'erp_post_views_count'.