Give it two weeks, the overcrowding issue will go down.
I honestly don't mind it really what was hilarious was during EA when the duty finder was down, everyone started grinding fates like mad
I fought in a battle against lazy Laurence it took just under two minutes to kill him TWO!
lol so many people it was freaking hilarious.

But yeah just give it a few weeks for the players to spread out.
It'll be fine.

Besides it seems like it would be a bit too complicated having varying difficulties.
with players dying, new players joining, random players just running through, the difficulty would be bouncing all over the place.