I know there was a thread on this earlier but I couldn't find it in the first few pages.
Our raid group hasn't made it past the first wing (yes, we suck compared to you world's firsters but we love each other and we're having fun).
One of the implied promises that Blizz made was that Siege would be less linear than the strings of circular rooms that were Tier 14 and Tier 15. The first 5 bosses have absolutely no alternate pathing possible. Does it open up later in the instance?