I think trusts are a great way to practice with classes or roles you may be unfamiliar with. I ran through each dungeon the first time with the trust party to see the unique dialogue and see the boss mechanics. Other than that I can't see myself using the system at all. The npcs just take too long, don't AOE, etc. I have only ever had one or two runs of a dungeon that took longer than it would have to run with a trust so as a whole it's not worth it to me.