i had the same problem, for my new site i just added a new meta "title" :

#functions.php

add_action('save_post', 'title_to_meta');

function title_to_meta($post_id)
{
    update_post_meta($post_id, 'title', get_the_title($post_id)); 
}

And then.. just add something like that :

$sub = array('relation' => 'OR');

$sub[] = array(
    'key'     => 'tags',
    'value'   => $_POST['q'],
    'compare' => 'LIKE',
);

$sub[] = array(
    'key'     => 'description',
    'value'   => $_POST['q'],
    'compare' => 'LIKE',
);

$sub[] = array(
    'key'     => 'title',
    'value'   => $_POST['q'],
    'compare' => 'LIKE',
);

$params['meta_query'] = $sub;

What do you think about this workaround ?

i had the same problem, for my new site i just added a new meta "title" :

functions.php

add_action('save_post', 'title_to_meta');

function title_to_meta($post_id)
{
    update_post_meta($post_id, 'title', get_the_title($post_id)); 
}

And then.. just add something like that :

$sub = array('relation' => 'OR');

$sub[] = array(
    'key'     => 'tags',
    'value'   => $_POST['q'],
    'compare' => 'LIKE',
);

$sub[] = array(
    'key'     => 'description',
    'value'   => $_POST['q'],
    'compare' => 'LIKE',
);

$sub[] = array(
    'key'     => 'title',
    'value'   => $_POST['q'],
    'compare' => 'LIKE',
);

$params['meta_query'] = $sub;

What do you think about this workaround ?