1) Change the CD of Riddle of Fire/Brotherhood to 120 seconds. Extend the duration of Brotherhood to 20 seconds and have it apply to all damage.
2) Remove the GL requirement of Tornado Kick and instead have it be something that can only be used every 3rd refreshing of GL (This also applies to refreshing caused by Riddle of Earth and Anatman) with a 30 second CD.
3) Change Anatman to only grant GL stacks every 3 seconds, regardless of server ticks and lower the CD to 30 seconds.
4) Change SSS into an oGCD that can only be used after a successful Tornado Kick and grant 10 seconds of True North upon its execution with no slow effect.
5) Either remove the True North effect from Riddle of Earth entirely, or reduce it down to 10 seconds at the most.
6) Remove the Fist Stances and untie GL4 from them. They offer nothing to the class and are fluff that can be removed entirely. They can also make the fist stances into just weaker versions of Riddles that change to riddles later on, with Fist of Wind becoming a trait to increase movement speed and Riddle of Wind being the trait to unlock the 2nd Should Tackle.
7) Have Brotherhood naturally generate 1 Chakra every 3 seconds for its duration while also still maintaining the extra chance to earn them from allies.
8) Change Deep Meditation into a 100% guaranteed chakra on crit.
With Brotherhood/Riddle of Fire being on a longer CD you lower MNK's DPS a bit but with the changes to Tornado Kick/SSS as well as the adjustments to Brotherhood and Deep Meditation, you are able to soften the overall nerfs to be less detrimental to MNK as a whole by smoothing out its toolkit in a way that makes it actually enjoyable to utilize your full kit. Tornado kick is no longer a dead skill but something that helps you by unlocking SSS to get another True North effect and with skills like Anatman and Riddle of Earth providing a faster build up towards TK, you can keep that flow going.
Personally, I don't feel that MNK really need a damage nerf all things considered. People say that its over performing because Brotherhood/Mantra is this god tier utility and that ignoring positionals is somehow busted but considering how little those skills actually offer and that the other melee DPS don't even have half the positionals of MNK, I just don't see that as justification for a nerf.