Well, some words are very specific, and others can change meaning depending on the context, so I don't think there are many "unnecessarily complicated" words.
For example, defenestration, in the context you're using it, describes a specific act, and perhaps you wouldn't add this word in your normal day vocabulary, but it could be useful for literature, academics etc.
Same with vicissitudes, it's not necessarily just "change", but can also be "an unwelcome change in your fortune"; the use of such specific words, depending on their contexts, makes the message you're trying to convey more precise and, well, uncomplicated! :]
But to add to your thread in some way, I've always thought the word "cavort" seems unnecessarily naughty, when it's quite innocent.
e: also, exploring the origin of certain words can sometimes explain why they came into existence, and then they don't seem unnecessarily complicated.
Post edited March 09, 2014 by cmdr_flashheart