Let's look at the state of our game. Every time a new champion is introduced, we all start jumping up and down because the concepts are fantastic, the abilities are cool and they are like nothing we've seen before...
Personally, I feel like Riot nails a champion when it comes to how strong they are, and then makes a few way too over powered, and then an occasional few just very ****py. I will use Darius as an example of being overpowered since release, and went through several hard nerfs to get him to where he is today. The second is Rengar. The recent nerfs to him were some of the biggest I have ever seen... For those of us who can't remember that week of hell when he first came out, I can assure you he was even stronger then than he is now. Even after those heavy nerfs he is still viable.
But what about Hecarim? He tends to be very overlooked by players, he's extremely fun to play, to play with (the really important part, this is a game after all,) and he's really balanced. Hecarim was right in between strong, but having exploitable fall backs too.
To sum up this post, I really can't tell for certain if Riot knows what balanced is but just don't always make their champions based on it, if they just don't know, or if heavy nerfs and buffs of new champions will just be normal. As for the newest champion, Elise, I will expect her to be left pretty much alone because she really isn't that insane- but her kit is really awesome.