Most party setups are viable if you're not worrying about time or some things for Relics. 17 min dungeon runs are tight even with optimal setups. Faction relics are hard enough as it is, non-optimal setups just make it harder.

I used to be all about wanting to play just Monk and was adamant about it being useful in all content. As a result I was told I was being selfish and that it was wasting everyone's time. I don't disagree with that statement one bit. We were struggling as it is and what we were doing was not friendly to Monks. Thus me being on Monk wasn't helping things in the slightest. We needed to figure out a strategy that worked for us first and get the fight down before we could try non-optimal setups. My options were: Suck it up and play what was needed (and come do things) or continue being stubborn and not get anywhere.

In all content there are some classes/jobs that are more efficient at fulfilling the needs of the party than others, that's just how it goes. Need AoE damage? Sorry, Aura Pulse isn't gonna cut it. Come DRG. Boss has 1-shot close range AoE? Melee are a liability, come ranged. Enemies are magic resistant? Sorry, can't use BLMs.

Now you can overcome all of those issues and start experimenting with non-optimal setups, I'm not saying it was impossible. Being able to change jobs at any time was not the issue however. You may not like changing to suit the needs of the party but our current system allows us that flexibility when we need it. You can actually work out and change strategies faster with this system because you don't have to go back to the city and waste a bunch of time just to change jobs.

A change I would support, however, would be locking classes/jobs once you enter content. That way you don't have all this switching around mid-run.