None of the above solutions worked for me when I tried to implement them. It seems that Telerik has provided an extremely simple solution to this involving an overlaid div as documented at: http://docs.telerik.com/kendo-ui/controls/editors/editor/how-to/enable-and-disable-editor
In practice this resulted in an extra div next to the control I wanted to disable:
<div ng-if="readonly/disabled_Condition == true">
<div id="overlay" style="width:100%;height:250px; top:100; position:absolute; background-color: black; opacity:0.1; z-index:2;"></div>
<textarea kendo-editor k-options="options.DutyEditor" ng-model="item.TasksHtml"></textarea>
</div>
The one issue is matching up the size of the overlaid div to the size of your kendo editor. In my case it's a simple 100% width and 250px height, so I lucked out here.
Thought this might help someone!