I find for one of the last temples in the game it is a bit to easy. I have never found it difficult because it is very linear, quite short, and The enemies are easy and there is very few of them. Alot of people find Bongo Bongo to be one of, if not, the hardest boss in the game and I dissagree. By the time you get to him (excluding 3-heart challenge) you already have alot of health which makes for a boss who does only a fair amount of damage to be a bit of a push over. I am not saying the temple is bad or is the worst temple. Just abit too easy for my liking.
I am one of the people who would say the Shadow Temple is one the harder dungeons in OOT. However no dungeon in OOT is hard at all. I would not argue that the Shadow Temple is difficult. I would just say that of the easy and moderately challenging dungeons in the game that the Shadow Temple is one of the harder ones. I would definitely agree that the Shadow Temple should have been more difficult since it is so late in the game.
The reason that I think the Shadow Temple is one of the harder dungeons in OOT is because Bongo Bongo is the hardest boss in the game IMO. I've played through the game probably 20 times and the one and only boss that has ever given me trouble is Bongo Bongo. I think it has to do with the fact that you only have a small window of time to hit the other hand once you hit one of the hands. My problem occurs when the Z-target doesn't capture the other hand and by then it is too late to avoid the hand flying at you and you get hit. Granted I would only die if I was doing a 3-heart run but that doesn't change the fact that from my perspective Bongo is the hardest boss because no other boss usually even touches me.