i haven't tested the following (exploit) recently but there was a time when re-rolling the map with a fire shrine was ideal for reducing his life to half . if that still works , then the fight can go below 1 minute (that was the real record) . if someone has the time and patience to re-roll the map , may test that .
let the gear in town , go to the proving grounds naked , open a TP in a safe area , summon near fire shrine , activate the shrine , die , get the gear on from town , go back in the proving grounds and rape him .