Just a thought. Less a proposal and more just a feedback/what are the downsides/upsides of doing this.
Perhaps it's just me, and it's NOT the worst offender by far, but I feel NIN has just a bit of button bloat, and this particular ability just...bugs me for some reason. It's a level 60 capstone ability, but it's also an ability that should GENERALLY never be used outside of (a) KO recovery or (b) an extended downtime (but less than 50 or so seconds) to prevent Huton falling off (or restore it after said downtime). So it has SOME uses, but...
...next to this we have Armor Crush, a branching -4 from your standard 1-2-(3) combo. When used as the third hit of the combo, it goes from 140/200(Flank) damage to 360/420(Flank) damage, increases Huton by 30 seconds (to a maximum of 60), and grants 15 Ninki Gauge.
Huraijin, by contrast, requires no combo, grants 60 seconds of Huton, 5 Ninki Gauge, and deals 200 damage regardless of position.
So just a THOUGHT:
What if instead of a separate ability, Huraijin was a Trait upgrade to Armor Crush? The upgrade would result in the following ability:
Huraijin
Weaponskill
Instant Cast
2.5 sec base recast
Range 3y / Radius 0y
(all the standard stuff)
Delivers an attack with a potency of 200.
Additional Effect: Grants Huton
Duration: 30s.
Increases Ninki Gauge by 5
Combo Action: Gust Slash
Combo Potency: 360
Flank Combo Potency: 420
Additional Effect: Grants Huton
Duration: 60s
Increases Ninki Gauge by 15
So, what does this DO?
In the first case, it allows applying Huton from nothing (no combo, just flat hitting the button at any time) for 30 seconds, mirroring what Huraijin does. In fact, it does the same thing Huraijin does now, just for half the duration.
In the second case, using it properly as a combo action, it gives the full duration of Huton, but requires using the proper prior two steps in the combo, meaning some forethought if the goal is to extend through a downtime longer than 30 seconds, and otherwise, it functions identically to Armor Crush right now. (We could also lower this to 30 seconds, that part doesn't matter as much I suppose, but I thought retaining that niche use wouldn't be a bad thing)
Now we've cut out one button almost never used (IDEALLY never used), while retaining its functionality. It's still a DPS loss to use it by itself, and un-comboed acts just like Huraijin does now, just for half the duration. Which shouldn't matter in most contexts since you should be refreshing it with the comboed version anyway, which you should use before extended downtimes as a finisher of your combo, so the skill ceiling isn't really altered here since you're exchanging a standalone extra button (hard because button, easy because no combo) for a non-extra button you're using at the end of a combo for this purpose.
I suppose the one quick critique might be that you use the -4 less so 1-2-3 more (making the duration only 30 sec either way handles that, though), and that some people might like the Armor Crush animation better and some people might like having a separate button for this...but...
Another critique might be that it makes it where you don't need to use Huton itself except in the pre-fight opener...but this is ALREADY the case from level 60 and above. Huton does no damage and costs you a Raiton (650 damage), and that 650 potency loss is going to be greater than any use of Huraijin as far as I can tell, meaning ifyou have to refresh Huton from a fall-off in battle, it will NEVER be with Huton under any circumstance in combat anyway unless you get raised INTO a 21+ second downtime (where Ninjutsu would have a full time to refresh after using it). So we're already at the point in the Job/game's life where you aren't doing a "naked" Huton refresh during fights anyway, not to mention if you did so, you'd get the full 60 seconds, making un-comboed Armor Crush-Huraijin's 30 sec still be a cost-benefit for you to make on the fly (though the answer would always be Huraijin as far as I can tell...)
I dunno, I'm sure there are arguments against it, so I thought I would post the idea and see what they were or if people would be like "No, this actually sounds good."
(Honestly, the only other thing I'd do with NIN is make Meisui an additional effect of Trick Attack since you have no reason to keep Suiton after using Trick Attack and it's kind of an extra button just to have an extra button...but their CDs don't line up. Could be an additional effect on Mug, though, but...meh. Beside the point, ignore.)