We're starting to need less stress testing and more "flow" testing - how enjoyable the game is as an experience from a progression point of view.
Then here's what you can do:
"There will now be a special item dropped at the end of the Naga City, but only games started after January 1st can get it,"
No anger over lost progress, but a carrot to get people to restart and test the progression.
Would you guys like some way to artificially increase difficulty in dungeons as an optional thing though? We've been lobbing an idea like that around for a while now and can't decide if we want to go forward on it or not.
I've been under the impression that this is exactly what dungeons like Grimm's Grotto and vicious Halls of Steel were all along.