Since the last months of Stormblood, I've made a goal to level all combat jobs to max level so I can experience all current endgame content. Despite the large variety of leveling methods SE has given us, and the systemic change to FATEs making them widely more feasible to level with, dungeons still currently remain the quickest way to level. I currently have all combat classes 71 and above, so I will be dungeon-running for a long stretch of time.
So far, I have done Holminster Switch, the level 71 dungeon, more times than I care to remember. I've done an amount of it with Trusts enough to level the 6 Trust NPCs to level 73, and I've done it on 7-8 other classes, 3 to 73, and the rest to 71.
I've heard accounts from people who have had their Trust runs take 30 to 35 minutes. I find that quite a bit long, and I can only assume those accounts are from players who are not good with their DPS rotations. The other number is 27 minutes. I don't know why, but this is the exact number of minutes, give or take a few seconds, that I always get with my own Trust runs if I try to complete the dungeon as quickly as I can.
A good, average dungeon run with players takes about 20 minutes. An almost perfect run takes 15 or less minutes, but that's rare with duty finder. I also have to mention that some runs can even take longer than 30 minutes, and this can be due to low DPS, people needing to AFK momentarily for IRL reasons, or a tank dying due to lack of proper cooldown usage or healing. It also needs to be mentioned that, taking into account queue time, it may take longer for a DPS (and momentarily with the rise of people trying out Gunbreaker) to even level overall. However, this is mitigated due to how good FATE leveling has been in ShB.
The Trust system provides a guaranteed method of leveling. It does not have the potential to be the quickest method of leveling at the moment, but the Trusts act in a predictable manner, making runs smooth. It is strange that I am complimenting a system designed for solo play in a MMO, but I feel compelled to do so because of experiences via Duty Finder that I find conflict with my playstyle.
The Duty Finder is great for first-time runs through dungeons, and at the very start of this expansion, the discovery of new environments and dungeon design was definitely enhanced by the fact that I shared that experience with 3 other unfamiliar people. However, when you do the same dungeons potentially 17 times more than the average player, exchanging pleasantries and risking failed runs due to conflicts in play style and skill may get in the way of other goals you may have as a player. As such, I do recommend Trusts for both new players to ShB and veteran players alike!