They can't turn duty finder off because:

1. It's the entire instance server - What this means if they turn it off you can't even do solo instances because people from 1.0 wanted everything in an instance, so enjoy.
2. You can't complete the story without doing duty finder even if you make a party beforehand.
3. You can't level in dungeons that aren't related to the story because you have to use the duty finder even again if you make a party before.

So, unless they make an update where Duty Finder is OPTIONAL, even if this was the cause they can never turn it off without interrupting most of the game's content.