First time ever suggesting anything. Not sure what'll come of it but here it goes:
The new Monk abilities in Stormblood are a step in the right direction but are falling short of where the changes in Heavensward brought us. In Heavensward you saw the weaknesses of the Monk class and applied that to the design of our abilities. Tornado Kick and Form Shift are utterly fantastic additions and really strengthened the core concept of building and maintaining GL - and offering us a dump option for pauses in the fight.
Stormblood has identified lingering weaknesses and tried to address them, but they are either not enough or add caveats for unknown reasons. I feel something along the lines of the following suggestions will help nudge the Monk class forward.
Fists of Fire:
At level 62 make the 5% damage increase a trait and change Fists of Fire to allow Bootshine to an extra 10-15% chance to trigger Deep Meditation. This will help with bad streaks of rng-dependent since Deep Meditation is based on two sets of rng (one for crit, one for chance off the crit).
Riddle of Fire:
Remove or reduce the skill speed loss and lower the damage buff accordingly. Allow for the usage of Tornado Kick without losing Chakra. Increase Tornado Kick cooldown to 20 seconds so it can only be used once.
Monks aren't a class that needs to hit hard. It's what we're told the very first time we speak to Hamon when we apply to join the pugilist guild. A hundred blows for every one of theirs. Giving Monks such a sudden drop in attack speed goes against everything we've played since 2.0.
The skill itself is a great concept though, burst for when we need it / replacement for Blood for Blood that we lost - it just needs tweaking because having the brakes suddenly slammed on is detrimental to the Monk playing style.
Fire Tackle:
Bigger potency - no stun. Choices are needed. A reason to be in one stance over another. Plus we get a Role specific stun.
Fists of Wind:
Movement speed unchanged. It's very niche and nigh useless, but it does offer a choice when mechanics are involved and choice is good.
Additional Effect: Lowers the GCD of Form Shift to that of Meditation.
Riddle of Wind:
Instantly adds 5 seconds to the GL timer and...
Resets cooldown of shoulder tackle...
Wind Tackle
...on use effect: Adds 5 seconds to the GL timer and 3 seconds to our current form (coeurl, raptor, opo-opo...)
Shares a cooldown with Riddle of Earth to avoid exploitation
This will, at most, give 10 seconds of GL, but staggered, unlike Riddle of Earth which gives a bulk amount of GL at once. This offers the MNK a choice between Fists of Wind or Earth.
Giving 3 seconds on our form timer will also save us from moments where we get to an enemy with 1-2 seconds of GL left but the GCD from the shoulder tackle prohibits us from performing Demolish or Snap Punch.
Fists of Earth
Same. It's a solid skill for boss mechanics where we no longer can hit the boss.
Riddle of Earth:
Keep this the same. If Fists of Wind is changes in any way to reflect the suggestions then the relationship between Fists of Wind and Earth becomes more entwined and allows for more adaptive playing style.
Earth Tackle
Increase stun to 4 seconds since Fists of Fire (in this suggestion) lost the stun.
Brotherhood
Love this skill. Not going to offer improvement as I haven't raided yet. But I wanted to close on a positive and this skill is inspired.