I've been joking around since trusts were announced that Estinien as a trust would only dive in to get the killing blow on the boss. But if they do go back and add trusts to earlier leveling dungeons it would be neat to be able to run dungeons with Haurchefant, Ysayle, Papalymo or Estinien.

. . . running the Vault for the first time with Haurchefant as a trust NPC might be a bit traumatic though.