I personally always watch the cutscenes/read the text the first time I encounter it anywhere in the game.
Tam Tara Spoiler…
A prime point, is in Tam-Tara Deepcroft HM - I read all the bloody parchments, as it gave you an insight into the degeneration of Edda, and why she was there. I feel that if you didn't read those, the experience would be lessened. Not only that, but skipping the end cutscene with evil Edda… well, people would be missing out!
I play the game for the story and experience, rather than to get the best equipment, or clear a dungeon/raid first.