Here is an import file where only a few settings are used (although you may be able to exclude even more), which successfully imports three posts (tested on WP 4.2.2):
<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0"
xmlns:excerpt="http://wordpress.org/export/1.2/excerpt/"
xmlns:content="http://purl.org/rss/1.0/modules/content/"
xmlns:wfw="http://wellformedweb.org/CommentAPI/"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:wp="http://wordpress.org/export/1.2/" >
<channel>
<wp:wxr_version>1.2</wp:wxr_version>
<item>
<title>My first post</title>
<dc:creator><![CDATA[admin]]></dc:creator>
<description></description>
<content:encoded><![CDATA[
<p>Welcome to my first post!</p>
]]></content:encoded>
<excerpt:encoded><![CDATA[]]></excerpt:encoded>
<wp:post_date>2015-03-01 16:20:00</wp:post_date>
<wp:status>publish</wp:status>
<wp:post_type>post</wp:post_type>
</item>
<item>
<title>My second post</title>
<dc:creator><![CDATA[admin]]></dc:creator>
<description></description>
<content:encoded><![CDATA[
<p>Welcome to my second post!</p>
]]></content:encoded>
<excerpt:encoded><![CDATA[]]></excerpt:encoded>
<wp:post_date>2015-03-02 16:20:00</wp:post_date>
<wp:status>publish</wp:status>
<wp:post_type>post</wp:post_type>
</item>
<item>
<title>My third post</title>
<dc:creator><![CDATA[admin]]></dc:creator>
<description></description>
<content:encoded><![CDATA[
<p>Welcome to my third post!</p>
]]></content:encoded>
<excerpt:encoded><![CDATA[]]></excerpt:encoded>
<wp:post_date>2015-03-03 16:20:00</wp:post_date>
<wp:status>publish</wp:status>
<wp:post_type>post</wp:post_type>
</item>
</channel>
</rss>