It's no secret that queue times in FFXIV, and mostly any MMO using the Trinity system, is directly linked to the availability of Tanks and Healers, while DPS have to just sit around and wait for them.
Is it that there are just not enough people playing Tanks and Healers? I don't think that's it.
The problem is that most people in FFXIV play MANY classes. And this, by its nature, means that you are likely leveling more DPS classes than tanks/healers.
This means that there will ALWAYS be a much higher amount of DPS in queue without enough tanks or healers to go around: because those tanks and healers are not "exclusively" playing tanks and healers. Most tanks and healers also play DPS, but a lot of DPS rarely/never play tank or healer.
So for example, lets say you are a tank main. And you usually play tank. But today you queue for DPS for some reason, perhaps you are just leveling a DPS today. Thats one less tank queueing for multiple roulettes today. Spread this likely event over hundreds of players and suddenly there are hundreds or thousands of potential tanks not in the queue. And its not the players fault, the system just forces you to choose only one role per duty per day.
This problem is then made even worse by the fact that most of the time when you ARE queuing for roulettes as a tank or healer, you are likely going with a premade group to carry some of your FC mates through the queue.
An easy solution to this is to add two NEW Duty roulettes to the daily system:
A Healer Roulette and a Tank Roulette.
These roulettes would have their own, separate rewards. And you can only queue for these SOLO. This would inject way more tanks and healers into the duty finder in a way that is rewarding for them; and it would likely reduce queue times for DPS at any level by a gigantic margin.
And because these roulettes are seperate alongside normal roulettes, it shouldn't INCREASE queue times for tanks or healers realistically, either. There would only be benefits by adding this into the game.