Is there a word or term for an attempt to simplify but which complicates instead?

While "deceptive" has many connotations, "deceptive" or "deceptively complicated" might help trigger the right alarm bells in your situation:

de·cep·tive

adjective /diˈseptiv/ 

1.Giving an appearance or impression different from the true one; misleading - he put the question with deceptive casualness

(deception) misrepresentation: a misleading falsehood

You might want to look at the word counterproductive.

EDIT:Just saw the update to the question. Some might balk at the usage, but Pyrrhic Solution seems to describe the interface.

The term false optimization came to mind when I read your initial post, and seems only more appropriate after your edit. I usually see it used in reference to actual performance optimization, but it can address the usability/process perspective as well.

Not exactly what you describe, but, in the context of software development, there are some related terms: overengineering, feature creep and scope creep. All of these terms denote the attempt to improve a product or project by adding more "stuff" to it. Usually, these additions are made with good intentions. But, despite the initial gain, they prove to be useless as well as a burden to maintain, in the long run.