I read an idea somewhere that I think would be cool: (Not my own idea) Select up to 3 or so people who registered for the duel. Those players will then be placed in a queue. The first player gets to duel the boss. If he/she dies, the boss resets and heals to full, and the next player gets to try, and so on and so forth. If all 3 players fail, the encounter despawns. If any of the 3 players manage to kill the boss, he/she gets the prize, and the encounter despawns.