Custom Rewrite Problem

You can try these rules:

reviews/([^/]+)/page/?([0-9]{1,})/?$
reviews/([^/]+)/?$

It’s informative to check out the active rewrite rules with:

function show_rewrite_rules( $rules ) {
    if(is_admin()) echo "<pre>".print_r($rules,true)."</pre>";
    return $rules;
}
add_filter('rewrite_rules_array','show_rewrite_rules');

and then visit /wp-admin/options-permalink.php.

There exists also some good plugins for analysing the rewrite rules, for example the Monkeyman Rewrite Analyzer.