You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <blocks>
      <block id="9" user="MAMargerete" by="Leupold" timestamp="2016-09-11T18:04:59Z" expiry="infinity" reason="Ungeeigneter Benutzername: Tippfehler" nocreate="" autoblock="" noemail="" />
      <block id="8" user="GS.Tenzer.Leoni" by="KSMehlem" timestamp="2015-09-23T19:05:24Z" expiry="infinity" reason="" nocreate="" autoblock="" />
      <block id="7" user="A.Burgermeister TEST" by="Karl Kirst" timestamp="2014-12-23T05:57:09Z" expiry="infinity" reason="Schutz vor möglichem Missbrauch" nocreate="" autoblock="" />
      <block id="6" user="A.Burgermeister (Test)" by="Karl Kirst" timestamp="2014-12-23T05:56:42Z" expiry="infinity" reason="Schutz vor möglichem Missbrauch" nocreate="" autoblock="" />
      <block id="5" user="A.Burgermeister" by="Karl Kirst" timestamp="2014-12-23T05:55:59Z" expiry="infinity" reason="Schutz vor möglichem Missbrauch" nocreate="" autoblock="" />
      <block id="3" user="MAAnna" by="Leupold" timestamp="2006-08-11T10:50:00Z" expiry="infinity" reason="Unsachgemäße Beiträge!" autoblock="" allowusertalk="" />
      <block id="2" user="JLeupold" by="Leupold" timestamp="2006-01-04T12:53:54Z" expiry="infinity" reason="" autoblock="" allowusertalk="" />
    </blocks>
  </query>
</api>