Restore Image Title Text

You can hook into the media_send_to_editor filter and add the title tag to the generated HTML image tag:

function wpse_78529_restore_image_title( $html, $id ) {

    /* retrieve the post object */
    $attachment = get_post( $id );

    /* if the title attribute is already present, bail early */
    if ( strpos( $html, 'title=" ) )
        return $html;

    /* retrieve the attached image attrbute */
    $image_title = esc_attr( $attachment->post_title );

    /* apply the title attribute to the image tag */
    return str_replace( "<img', '<img title="' . $image_title . '" ', $html );      
}
add_filter( 'media_send_to_editor', 'wpse_78529_restore_image_title', 15, 2 );