Here's a video of how we completed the lvl 81 Rune labyrinth in a sps/ee duo setup. After several mediocre attempts, we did manage to finish the dungeon in, I would say, a reasonable time of ~30 minutes. The damage is limited due to the nature of the class, but I think that further improvements could still be made on the gear and mana management so that times of ~20 minutes could be reached.
GL&HF!