Pretty sure it'd still be a lot of work.
It'd just be "different" work - no need to create new scenes, write plots or record voice acting. But there would probably be a lot of new coding involved, especially if they adjust the enemies to scale to level.
People seem to not understand that code base for a modern MMO is gigantic, developed over years by many different players, and under changing requirements. In other words, it's probably a Gordian Knot of interdependencies where virtually nothing is "a simple change", not even if you spec'ed and designed the change in advance. Which is precisely why when they fix a bug it sometimes triggers a new bug or the resurgence of an old bug.