But people are understandably cautious about going with non core code. The Cloze GUI is very good
https://moodle.org/plugins/pluginversions.php?plugin=tinymce_clozeeditor
but its not core.
The other options you mention (OU Question Types) are excellent in terms of features and support but they are not core.
At the Edinburgh Moodle Moot 2014 I asked a room full of about 80 Attendees "who here can type out Cloze Syntax 'off the top of their head'" and one person put up their hands, that person was Michael de Raadt (person in charge of development at Moodle HQ). This is a mountain sized usability issue in core Moodle.
I took a look at the install of an organisation that teaches languages amongst other things and they had 60,000 multiple choice questions and 750 Cloze questions, I think that tells a story.
Cloze or Cloze style question types needs fixing in Moodle Core not through addons.
(Andreas and German are you planning/working on a 2.7/Atto version?)