I normally don't post here, but what they're deciding to do with ninja is actually pretty infuriating. For context I'm a ninja main and have been since a realm reborn. Now with that out of the way, let's talk.
Right now Ninja is in the same position that Stormblood Dark Knight was. It's incredibly high skill cap but not very rewarding. That's not to say the job is bad, it's just not worth playing in terms of how complex/difficult it is.
TCJ needs to change. Innocence and Titan (New) are a prime example of why it needs to change. This is one of the most mobile jobs in the game. We have fleet of foot. We get not one, but two uses of Shukuchi. We can move during literally any other skill. The amount of time you have to sit there for it to fully go off is completely unnecessary and beyond unreasonable. If you have during the cast, you lose the skill. If you get knocked back, you lose the skill. There are two possible suggestions I can give here. The first is pretty obvious but the dev team seems extremely adamant against this one: Let us move during TCJ. That's it.
The second and less obvious one but more preferable: Let us skip the Ninjutsu key. This will still make us be forced to sit there, but for a far more reasonable amount of time. This won't even effect the combination as we just hit 3 mudras and set them off as we use them anyways. This is also a slight dps gain.
Secondly, let's talk about Meisui. This skill is just.. not good. Unless you use TCJ to cast it, you're actually losing out on potency. Not only that, it's just mug without a potency and an additional requirement. Firstly you could: Give all 80 ninki gain to mug and change Meisui's ability. There's no reason to have to abilities that do essentially the same thing and there's no reason you should have to question whether or not an ability is worth using and the answer should also never be "barely". Make Meisui buff your next Suiton with an obvious potency gain and get rid of the requirement of having to have Suiton up. This lets us have options of TCJ instead of being forced to use it on Meisui whenever it's up. It's not interesting gameplay.
The second and more preferable option is: Don't make Mesui dispel suiton. Make it a requirement that it's up, but don't make it eat the skill. It's self explanatory. Needing to cast Suiton to use this skill is what makes it bad. If we remove the need to cast it twice, it fixes the dilemma. This is probably the more preferable option. This way it can keep itself aligned with trick attack.
Basically: Potency buffs aren't necessarily needed. Just move some stuff around with the skills and we'll have innate buffs and the job will feel more rewarding to play.
I'm not even going to get into ping and how badly it affects this job. I pretty much just want to address these two skills. Other than that I'm definitely happy with Ninja this expansion, even if we're not in a spot where we want to be.