Hello,
This is difficult because the ninja is easily sweepable. Yes I saw that you said not to tell you to sweep but this is the easy way to do it. I suspect that you may have done the breakthrough improperly. If I recall correctly, the correct order to do his skillbreaks is

Mystery = Passive 2 > Chase > Passive 1 > Standard

This order is based on rarity, NOT value. Using this method, while not guaranteed since RNG always factors into these things, tends to result in fewer vials used because it locks rare skills first and common skills last, making it, on average, cheaper to skill break the unit. It seems that you saved some of the rarer skills for last and locked one of the more common skills first, which will result in an overall waste of vials, which is probably why you spent so many.

In addition, I'm not sure where you got your vials, but if you get them from great plates they come out to about 15 coupons per vial, much cheaper than elsewhere, making them generally much more affordable.

Finally, as mentioned previously, you should just sweep for him. Your stamina may be precious, but nothing but ingots is more precious than coupons, so if this skillbreak is important to you, use the stamina to finish him. It would be recommended to use the fragments to finish his last skillbreak once the others are finished to save on vials. Hopefully this helps.

In direct answer to your question, it is unlikely that the devs will nerf the skillbreak RNG of this specific ninja for you in response to your..poor luck with vial RNG. Apologies, but best of luck!