I think the boss in Air Temple wasn't too hard, as my team was very strong from items and being high level. The first boss and the wind girl feel like the strongest ones and tough in the first encounter, but I like it. The pirate feels a bit weak, but I'm not sure if that's because I usually defeat wind girl before. Oh, and the optional boss is very tough. I had to go farm other bosses in the last run after failing to defeat him, but I've defeated him before at first try with a different team. So I think it's good because even if he's too strong you can just go back later.