The problem here is that such optimization has very little impact on the actual total clear time, even as a PLD. It's less than a minute or two for the entire dungeon.
I simply don't play the game to be on the edge of my seat, mashing buttons trying to achieve that 99th percentile. I'm sorry, but I play games for fun, and shaving 5 seconds off of a boss fight is really not something that really matters to me much, and if it mattered to the other 3 people in Duty Finder, then maybe they shouldn't Duty Finder. Maybe they should run with their Ultimate/Savage FCs instead if they want their 10 minute clears.
Some people need to just chill and lighten up and understand that not everybody worships parsers and damage meters, and they just wanna chill in a MSQ dungeon, expert, trials roulette, whatever.
Now, of course, we don't need people doing like 30-50% of their possible DPS, well obviously. But losing 10% DPS because you're not mashing the buttons so that you squeeze 0.1s between attacks, or going for <0.2s time between an ability is available and using said ability, etc... doing that constantly is exhausting, and simply not fun especially when there's very little need to do that.
I mean... IRL, when you go shopping, do you run full speed down the aisles, and hurry hurry hurry grab everything you need, run back up, and hurry and dump everything on the checkout belt and have everything ready to go so you can hurry hurry hurry out the door, etc? No, of course not.
There's a time to hurry and there's a time to relax a bit. In fact, this insistence on being 100% optimal and doing things 100% right at all times is why most people don't think too highly of Savage/Ultimate players. I mean, do you guys do this with non-instanced quest mobs, too, where you run 100% optimal rotations for every open world fight, too? I can't imagine trying to play like that, just seems so pointless to get that mob dead 0.5 seconds faster.