Last year we had an obstructed view cabin on emerald deck on the Emerald Princess. Part of the view was obstructed by a life boat but to be honest we were in our cabin for so little time it was not a problem. For me the main benefit of a outside cabin is the natural light and not necessarily the view which you can enjoy from on deck.Obstructed view cabins tend to be a little cheaper.
Yes we had tender boats obstructing our cabin view couldint see a thing we asked for a move and got the third deck with port holes but the view was good that was on the island escape.
With careful examination of the deck plans, matching up the lift shafts, and exterior photos it is possible to ascertain which cabins have a window situated between two lifeboats which means you could at least have some sort of view and extra light. These cabins are inset from the outer edges of the ship so you will find the deck above you (or possibly 2 above) will block any direct sunlight but at least you will get some natural light into the cabin. You also have to consider how much time you will spend in your cabin. As you are going to the fjords you will probably spend quite a lot of time out on deck as even with an unobstructed view you wouldn't get to see the all the sights as you cruise along. Hope this helps.