Just read the LJ side of things. Your idea of "the two dwarves enter into a power struggle for leadership of the team" creates a perfect story conflict because the story question is very clear, and the 5th Blight is just the setting rather than the story. If you tackle it linearly, the only scenes you need to focus on are ones that move the story question forward. Trips to Dalish (or wherever) might be glossed over in a scene or two.

One thing that might help is making a list of all the reasons why Aeducan and Brosca struggle for power and then select portions of the 5th Blight that best illustrate the struggle conflict ratcheting up. Also think about who will change (Aeducan? Brosca? Both?), what forces the change, and how it turns out, and then pin point the scene in DA:O where that change happens. That becomes your story's climax, and that climax might be completely independent of DA:O's climax. Everything after that is wrap up and dénouement, and can be summarized rather than plodded through. (This is the approach I'm taking in my Cullen-as-a-recruitable-companion version if DA:O because telling all of DA:O would be far too much.)