So this is my final idea after combining other peoples suggestions:
After lets say I make it to the boss 10 times with the regular rooms (which means I “learned” the rooms) I receive a certain number of(2-3) special ambers to use which if I use those puts me right at the boss.
Until I run out of those special ambers I can retry the boss immediately. When I run out I have to use normal ambers to redo the crucible the normal way. And from that point on I can get more special ambers if I make it to the boss. If I kill the boss it spends all of the special embers so I have to go through the rooms again.
This gives players who “learned” the dungeon rooms more tries at the boss without it being boring. This also ensures there is some amount of padding. You have to go through the rooms once in a while after “learning” so you prove that you are still worthy of challenging the boss.