Just two points I want to focus on most:
Because increasing GCD speed just another way of increasing damage gains by making your attacks come out faster. It's the same dynamic as early ShB, what is better GL3 and FoF or GL4 with FoW.
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[You could allow for a choice between Damage and Attack Speed], but you create a situation, especially between FoF and FoW that will come out on top as mathematically better. So whilst it is a nice idea, I don't see it really working out.
They're not exactly the same, though, especially so long as you return timers to Disciplined Fist and Demolish, though there may, yes, be a best choice in each GCD.
Skills with high individual damage are best used under damage buffs. Everything else is best used under speed to increase the portion of uptime spent on stronger skills, because amping the weaker skills by 5% is not worth as much as getting through them 5.3% (actually quantized by durations, but this is just a spherical cow) faster and thereby increasing the portion of stronger skills that are then further amplified.
Like, if we want the stances to be choices at all, then we're going need to have...
- branching paths that still ultimately (though in complicated fashion) have a best answer or
- clear best answers across a 60- or 120-second period (due to Blitz, Disciplined, and Demolish line-ups), or
- at minimum, preferred stances for each action (Wind for low-pppgcd [personal potency per gcd] skills, Fire for high potency-GCDs where oGCDs in gap are obviously included),
or...
- as before, Wind and Earth are dps losses used only as a last resort and rarely able to make any real difference to survivability or mobility anyways (unless you amp the hell out of them, risking making Earth OP overall, or redesign them to use a sort of granular resource)...
- at which point, you might as well have Wind and Earth consume MP and remove Fire altogether, or
- turn Fists of Fire into your granular Riddle of Fire phase -- perhaps only affecting beast skills or adding flat potency if worried about them being overly obligatory for oGCDs and/or Blitz or applying some other way to force stance-rotation, such as, idk, ramping drain costs from staying in a given stance too long.
Whatever the case, adding that allows for some small-gap skill-expression akin to Shadowbringers positionals for those who like a stick-shift feel that's less hamfisted and not nearly so wasteful as Shadowbringers' stances.
Then Monk would need a way to build up MP and it would effectively be a build and spend when full, unless damage is linearly proportional to the MP spent so that it doesn't matter. However, the bigger thing here is that by de-coupling it from Perfect Balance, you turn it into just another attack with no real meaning behind it.
Just a thought, not necessarily for the same exact context. Meanwhile, that MP generation could come from, in essence, standard rotation, such that you can have a rushed rotation creating burst phases and conserve phases between. Granted, the last thing we'd want is even more Opo-opo spam, so, it'd have to be for a different structure anyways. Hmm...
How many people choose not to take Monk or Reaper into Criterion Savage Dungeons or say they are an issue?
Not many. My point, though, was just that it's a raid-scaled skill that at best gets up to, well, flat potency damage that'd normally be the baseline, and is sort of the opposite of support thematically (everyone supports the Bard, instead of the Bard supporting others).