How to make Labyrinth more rewarding...

How about adding an Enchant Reroll Artifact behind the Silver Doors? This could give players a choice between a straight speed run vs exploring more of the side areas. Another, or an additional, option could be to trade in # Silver Keys for an Enchant Reroll (eg: 3 Keys per reroll). This gives a 3rd option of just grabbing the keys for an additional roll. So,

Speed run: 1 roll, fastest run
# Keys: 1 reroll
Artifacts: 1 reroll per Artifact, slowest run