Dungeon World

[Eyes of Nine]

I'm having a heck of a time challenging a party of 3 adventurers in Dungeon World. They can defeat any monster in the book with minimal effort. The cleric can heal any number of wounds using a Rote and expending zero resources. They are now 6th-7th level, and there is absolutely no challenge in the game. There has really been no threat of death throughout the campaign, with one character making the "cheat death" move (or whatever it's called). And he succeeded.
Am I just missing something?

I found in my campaign that yes, as they got higher levels, they were less likely to fail in the things they were good at. That said, I had 2 characters die. They key is to use the GM moves to do more than just direct damage; and use the 7-9 results to whittle away at their resources. Yes, they can use a Ritual to heal; but you can add in the fiction that there has to be a sacrifice of some sort. Their god demands it.