First of all it is important to understand succession musa as a whole, many people get scared by his damage, which is indeed very high, but it is still an underplayed and overall underperforming spec for PvP. So how can a top tier damage class be underplayed? There must be a reason, right? On practice damage is literally the only resource succ musa can be proud of, on every other aspect he can be considered either average or most likely under average, then, even to apply his damage becomes an excessively hard task. Let's go through his kit resources one by one:
PS: Keep in mind, I am just explaining weaknesses, not asking for all of them to be solved.

1. Iframes -> This is pretty much a former downside from musa, not much to say, we have a 3s CD one on dash, but we need to keep dashing pretty much all the time, so it is kinda unviable iframe, also bow iframe which has 13s CD, but it is gapped on the beginning (on charged arrow) and on the end due to arrow cast. This means he has a hard time avoiding damage and grabs from other classes at melee range, but he basically needs to be at melee range to use his best CCs and all his damage tools as well, which kinda helps to justify his high damage burst.

2. Grabless -> This for sure does not need improvement.

3. Mobility -> Well this should be musa former strength, but in succ musa case, it is easy to say he is not an S tier or even like A+ mobility class. When it comes to protection in mobility it is very good, speed wise it is not bad neither (but it is heavily affected by slows), though when it comes to sustain, by that I mean stamina, it is for sure one of the worst out there. Succession Musa uses stamina for movement, catches and even for combos (damage), meanwhile only Rising Storm (and its flow with 25s CD) allow SA stamina recovering, by that you have a kit that uses stamina for everything but has even more trouble trying to recover it, being easily pressured by other decent mobility classes and also uncapable of chasing them most part of the time.

4. Protection -> Like I said before, succ musa is very protected mobility wise, though when it comes to other aspects of the kit (CCs and Damage), it is safe to say it is one of the most risky on the actual meta. Since BON release, it is very hard to find a spec that does not have acess to at least a single Super Armour CC and that is succ musa case, the most protected CCs you got are two Frontal Guard ones, so if you want to CC someone you are going to expose your self 100% of the time, that also affects our combos since re CCs will always leave openings too. When it comes to damage, blooming and cyclone are essential to reach the class maximum output, both are unprotected and due to the blue buff mechanic, plus the way succ musa functions as a whole, you normally end up using these more than once per combo. 

5. CC Kit -> As in protection topic, succ musa CC kit gives the idea of playing on 2019 game, that means it is not really bad, since it is fast, but it is out of the actual standards of the game. Succ musa as a non-grab class, again, has not a single SA CC, but also no blockjump neither easy frontal guard piercing skills, by that I mean those that simply ignore Frontal Guards passing through it (spiral cannon from strikers i.e.). Other than that, knockdowns are also nearly unviable for succ musa, since the only one you have is an unprotected kick that does not flow well with the rest of the kit, also making you unnable to use air attack modifiers (a big part of succ musa burst), that by itself already helps to balance his damage out too.

6. BSRs -> That is more of a general balance issue of the game, since it happens to many classes, but just to mention succ musa also has a pretty scuffed 100% skill, which unironically deals less damage than the pre awk version.

All those weaknesses are commonly used as a "way to justify his high damage", but in practice it has come to the point where it is exaggerated. To illustrate that, I will be comparing him with other classes as a matter of example, since it is a balance discussion. 

Succ dk is the best one for that in my opinion, since she basically has the same niche as succ musa (fast, high damage, melee class), both damage are extremely high, but most of the weaknesses above are simply not applied to succ dk. She has way better stamina management, being able to recover during multiple SAs and not depending on it for damage skills i.e., she has blockjumps, she has multiple SA CCs, she has good and big amount of iframes and also decent access to knockdowns. I am not saying succ musa should have all of these and it would be fine, not that succ dk is fine neither, but I am showing two opposite extremes in terms of balance, it seems like for her being grabless is enough to justify having any resource, while succ musa wise your basically lacking most of the resources available, grab just being one of them. That is just one example (the best in my opinion), but even when you take awakening musa that also has way better stamina, protection, KDs and a SA CC with 6s CD while still having very good damage or most of the other fast classes like succ ninja, awk nova, etc... Succ musa costs become pointless.

Another interesting point of comparison would be other heavy stamina starved classes, you could take post nerf succ kuno i.e., which I think stamina costs are also across the board to be honest, specially since even her Q block costs stamina. Not saying that she is the standard of a good class or anything, but compared to succ musa her stamina costs make way more sense since she has blockjump, multiple SA CCs, grab and decent access to iframes. When you compare her to the rest of the game tough, it is also unfair, since you have other classes with these resources having way easier time stamina wise. Stamina is an overall poorly balanced resource across the game.

Conclusion:
To conclude, my suggestion is to improve a single one of these aspects, stamina. Considering a grabless class, that depends on unprotected damage and CCs to perform, I think it is fair to at least give him better time to work around his great strength and his set of weaknesses. So please consider, allowing stamina recovering on Prime: Backstep Slash, Prime: Fiery Angel and/or even Prime: Gale linger (it should have costs on blue buff use). Maybe also reducing/removing costs from some of the unprotected CC skills like Prime: Carver (120), Arrow Grapple (200), Prime: Blind Slash (100) and Blind Thrust (100). This already would make the class feel much more comfortable while still being non-grab, nearly non iframe and risky enough to justify his damage out.

PS: Sorry for any grammatical errors, not a native english speaker.

The only thing musa needs is hard nerfs in PvP

just to make sure you do realize he is talking about succession not awaken right? they are very different.

nice argument kekw

Nice argument bro

btw my spec is not even on the list kek

Thankfully OP listed a prof that succ musa is exactly avarage tier, so is balanced, no buffs are needed. Out from the 46 specs in the game, succ musa was 26th, which is right in the balanced category acording to raw statistical numbers.

well the first to talk about unrelated spec was you, but statistical numbers for avg participation between 46 specs should be around 2,2%, so no it is not average (avg-low at max), neither the worst spec on the game. But I can only talk about classes I understand, recommend you to do the same. ;)

so again why are you highlighting awaken musa when we tried telling you we are talking about succession?

Stamina lock removal from Fiery Angel and Back Step Slash is such a dream ahhhhh