A recommendation regarding the vanishing platforms: Hold and charge spels, or bow if you miss them. That will make you fall extremely slowly, giving you an opportunity to wait for them to re-appear.
This and Hagers Cavern were the most annoying locations in this game. The Spindlebeasts are too tough, platforming was ok, but once youre on top (sanctuary) how are you supposed to go down safely? I died more going down again to the boss than the boss itself.