I agree that this decision sucks. Even taking DPS queues into account, you'll still level faster if you do FATES while waiting in queue than you will by spamming Trust. And since the FATE rewards are pretty cool, there's even more incentive to level that way. I really hate it, because there are times when I really can't face running a dungeon with strangers and I'd rather run with my Trust party, but it's just not worth the pain. I really hope the devs will change this. They should just make it so that the Trust party levels as fast as the player. That seems like a good compromise.