That sounds like awful design.

Just make the trusts my level. Whatever my level is at the moment, that's the level they are. That's actually EXACTLY how it works in FFXI (where this system comes from).

Basically if I want to level with trusts, I can't do that. If it takes 12 runs to get 3 of them to the next dungeon that's absurd. For one thing it's not going to take ME any 12 runs to level that high. So I'm going to massively outlevel my trusts AND be unable to proceed to the next dungeon in the sequence if I want to bring them along. The only other way to do it would be to evenly level all my jobs to keep in range of the trusts and that just sounds horrible.