Sounds very complicated to me. You need to implement this for every dungeon with specific detail since on 1 dungeon you start on a boss, on the next dungeon you do 75% of trashcount before you see the 1st boss. There are dungeons where you can not even know which boss is the 1st boss because of freedom, etc.
You completely ignored my argument of the behaviour of players will change when a leaversystem gets implemented.