Hi lmsalter57, and welcome to cruise-chat.
I don't know if you've booked your cabin yet, but I wanted to answer your question about the duties of the concierge. We had a wonderful concierge on a different NCL ship a year ago. We didn't utilize the service much, other than to have her make reservations for us in the specialty restaurants. That might not sound like a huge deal, yet she knew in advance of a conflict our preferred time would have with the Captain's Suite Guest party, so she let us know and then changed us to a different time. She also visited daily to find out if all was OK, and if there was anything she could do. Now, this was a small ship, so I don't know how this would work on Norwegian Dawn. Other perks we enjoyed with the suite were priority embarkation and disembarkation. But, the main reason we booked it was for the size of the cabin, as there were three of us (myself, husband, and teenaged son).
Yet, a 205 square-foot cabin is certainly roomy if there are just two of you, and the BAs are in good locations on the ship. Whether it's worth the extra money for more room is up to you--there's really no right answer.
Good luck with your decision, and let us know how it turns out!