functions.php

<?php

/**
 * Change DPS titles to h3
 * 
 */
function be_dps_titles_to_h3( $output, $original_atts, $image, $title, $date, $excerpt, $inner_wrapper, $content, $class ) {
  return str_replace( $title, '<h3>' . $title . '</h3>', $output );
}
add_filter( 'display_posts_shortcode_output', 'be_dps_titles_to_h3', 10, 9 );