WYSIWYG filter - Anchors get wiped out
According to the WYSIWYG Filter module page it follows TinyMCE valid elements syntax. From that page: 


  ! Makes attributes required. If none of the required attributes are
  set, the element will be removed. For example, "!href".


It looks like your attribute string uses the exclamation mark to make the 'href' attribute required but the &lt;a&gt; tag you're putting in your content does not have that attribute so the element is being removed.