I don't know how work is divided at Bioware but it's believable that, if nothing else, they transferred to other teams to work on other project.
That said, what matters is whether the final result is acceptable or not.
I've wondered - considering the short development time and this is pure speculation - if Bioware had a plan for a Dragon Age direct sequel and EA wanted a DA followup in a short turnaround time and so they created a side-story that could set things up for the bigger story, shaved off a small team who, as their jobs wrapped, moved back to the other DA sequel team.
Still the reused maps didn't bother me - its not like my game enjoyment is tied up into how amazingly twisty the caverns are.