docs(Custom directives to access DOM): improve readability

When I first read the "Custom directives to access DOM"  I thought the wording was a little confusing.

I still dislike the wording "artifacts that access the DOM are hard to test" because tools like Protractor makes it pretty easy. Perhaps a better explanation would somehow explain that DOM manipulation outside of directives creates tight coupling that decreases testability, which is obviously undesirable.  Is it worth trying to include a sentence like this, or is the current definition sufficient?