Why not? The game was plenty broken before it, its actually a lot better balanced now with these changes.
Oh don't even get me started on how broken the game is!
I dunno, it looks to me like they have skirted around the real problem, the ai. It needs serious fixing as currently the only way the ai wins is by putting the difficulty up so much that its spamming armies out of its arse by cheating.
Most of the fixes are things that were right at the bottom of everyone's lists like embarking units showing as 500 strength, I hadn't even noticed that to tell you the truth.
STRATEGIC AI
Prevent AI from building too many AA units
Don't allow CSs to build Manhattan Project
AI calculation of enemy military might are tweaked based on size of enemy gold reserve
AI calculation of enemy power now takes into account promotions
All but the ai AA unit spam fix is just cosmetic and could be done much later.
Ai diplomacy looks unchanged imo as the ai was still a dick before the whole denouncing thing so changing it so they don't all denounce the same person all at once probably won't change a huge amount. Just cosmetic again.
Multiplayer is so broken that those changes just aren't even worth the bother from what i've heard. Haven't tried it my self.
As for the balancing, on paper it just looks like they have removed some food and gold while lowering gold maintenance while reducing the hammers in some cases and boosting it in others. As I said, on paper it doesn't look very nice to me but obviously it may play differently to how it looks.
:EDIT:
I would say it looks like the positioning of your city is now more important as a well placed production city will be fine but those without production in easy reach are going to suffer badly. This is not a good thing as there are many places where there is limited production but a luxury resource you need. Top this off with the reduced happyness and it looks like its made it harder for the player while the ai will be able to ignore all this and spam cities like always.
Fixing the ai city spam should be the first thing on their list of things to do.