While the RadEditor is able to now be used on Mobile devices more easily, the crux of the WYSIWYG for us is that when creating either HTML for web or emails, the HTML that is generated from the RadEditor doesn't always generate the code that follows or renders correctly on mobile devices. Ideally, the respective HTML that is generated is correctly output in Mobile Responsive format for all mobile devices.
Can you please provide more details about the HTML you want produced by the control? What types of tags, styles do you expect to see produced. For example do you expect the tables to have applied width="100%", the images to have min-width and max-width. BTW have you tried to tweak the produced HTML markup by RadEditor using its custom content filter functionality: http://demos.telerik.com/aspnet-ajax/editor/examples/contentfilters/defaultcs.aspx?