I like trusts as they are just for dungeons. I think it's good there is some content you just can't do with them, makes sense in lore as characters would become tempered if facing Primals.
In dungeons there is a lot of scenery and mobs to see so it's a good feature there to let you appreciate developer's work. I worry about all Duty's becoming "farm mode" if they take it too far though, it's good to see people work together and figure stuff out sometimes, like wipes on Shinryu tidal wave and such.