Temple of Three was a backer area apparently. I haven't done it myself yet but I've already heard of how it's now universally considered the worst part of the game. Blackwater was also a backer area.
The concept of backer dungeons needs to get shot into the sun to be honest, or at least a lot more scrutinized. Blackwater was admittedly rather neat, I think the only real problem was that the game just made it possible for you to go there way too early (it should have been a late chapter 3/start of chapter 5 dungeon instead of being available at the start of chapter 3). But you were given free reign to design something, and you go with rather gimmick fights instead of something that could have had neat reactivity with deity background choices and all of the mythic paths.
As for the difficulty... The further I get, the more I realize that the game is just expecting you to optimize all of your companions at once, at least on Core difficulty. In most other cRPGs, I could get away with only really caring about the main character. Both of the Pathfinder games won't let you do that.
Also, the memes on the Pathfinder subreddit are -amazing-. The great thing about the focus on the party banter and the large varied cast of party members is that the community there is going to have material for years.
