Exaggerating is already over the top. That's the point of it. I have the sneaking suspicion that over-exaggerate was created by the department of redundancy department.
Synonyms are all good and well. But they aren't exact synonyms. Let's say I were to type a word into Microsoft Word and select its synonyms. For this example let's use crazy. So I type crazy in and see a list of its synonyms: mad, wild, passionate, extreme, fanatical, foolish, unwise. Yes, all of those can have the same meaning, but they aren't completely synonymous. Fanatical can mean extreme devotion, mad can mean angry and is only used in certain parts of the world to mean crazy, wild has a huge number of uses, same with passionate. Synonyms are wonderful things, but only when they offer variety. When you wind up just using more syllables to say the same thing you're doing something wrong, and wasting precious seconds of people's lives.
Let's add a new one to the list, literally. As it is it is a wonderful word that can certainly clear up issues with distinguishing between an exaggeration (on ground level, not over anything) or a metaphor and something that actually happened. I actually make sure to take things too literally in my mind, purely to visualize the hilarious things people say sometimes without ever realizing it. However, literally has become the pet word of preppy high school girls, at least in my state, and it is starting to rival "like" in number of times used during a conversation. If you are telling a story, and state a fact, I am more than likely going to believe it was literal. You don't have to tell me her boyfriend was literally right there. If you just said that her boyfriend was right there I would have believed you. Honest.
Luckily literally isn't quite as bad as "I'm not gonna lie." Another phrase useful in moderation, but that gets taken to extremes. I'm sorry, but if you really have to say "I'm not gonna lie" multiple times in a conversation you're probably a pathological liar. Let me reiterate. Unless you are telling blatant lies, or have my a curly black moustache, I am probably going to believe what you tell me without constant clarification that you are not lying.