Arena is getting harder, but that's largely because players are getting better. There are no set templates to play from because of the randomness of the picks. Granted that experienced players who get lucky with picks will get further than less lucky players, but on the whole the playing field is fairer in arenas and I feel that laerning the game works better there, plus it is guaranteed to earn you some cards, no matter how badly it might go. On top of that there does seem to be a clear difference between how effective hero powers are in Arena.
Constructed does indeed feel broken, especially when you're new to the game. However, there are some ways around it. A sure way (but this does require copying a decklist) is to go with the complete free to play pally deck. This is a very solid, well-rounded deck which guarantees you at least some success. I'm sure there are other budget decks out there which will work well, if not better than the expensive ones.But hey, it is still a CCG, that comes with the nature of the game. If anything I think Hearthstone is fairer in this aspect than say.... Magic the Gathering is.
Hell, my most successful deck has no epics or legendaries in it but still performs very well. It would perform better with certain legendaries in it which I don't have, but that's ok. Like I said, it's a CCG before it is a computer game, and the initital hurdles inherent to any CCG must first be overcome before it becomes a lot of fun.
As of yet I have also spent no money on the game. What cards I needed for ceratin deck ideas I got in arena packs and through crafting, the materail for which are also to be won in arena.