You should be able to edit most of the content in the visual editor. While I try to create shortcodes which involve “complex” markup, converting everything into shortcodes is something that limits the user’s ability to customise content and can make your code too much dependent on the theme you load. While you can use the visual editor most of the time when editing a page, some times you may want to switch to html editor(or text editor as seen here) as seen here –
http://lorelleteaches.com/2012/10/25/how-to-add-html-in-a-wordpress-blog-post/
to better control the content. You should never have any problems editing the code in the HTML editor at least. If you have issues, pls reply as a private message here with the site URL and a temporary login to the WordPress dashboard and I can take a look. You may also email me the same (see bottom right box in my profile page).