Sooo 3 things
One how to shatter bosses? I tried everything with no avail
2 when will we use the dungeons again?
That's two things ;)
1. You can Shatter Boss Girls by reducing their HP and WP to their lowest point and then winning the Clash (It's a finishing move, basically).
2. No ETA on the dungeon returning - the whole thing needs a rework so that it isn't A) endlessly repeating poses, and B) doesn't pile so much work on me that the game takes another five years to complete :P