Few things:
  1. My toolbox has two calculators that factor in debuffs (simple and advanced). You should be using the simple one, at the very least. That will tell you that Amaterasu yields an overall DPS boost (or break even) due to the massive benefit of -20% DEF. Not only that, she increases survivability with her -20% ATK, regen, and DEF buff. The Advanced calculator factors in buff/debuff uptime, but requires more setup time.
  2. The Advanced calculator DOES factor in damage skills. It's set to the skills of my team by default, but you can substitute in your team's skills if you know (or can guess) the damage multipliers.
  3. The simple buff/debuff calculator features a basic survivability calculator that compares the effects of the various buffs/debuffs on incoming damage and how many hits your kamihime would be able to take before dying. It sounds like even Aidoru might benefit from taking a look at this.
  4. You're drawing erroneous general conclusions from your bad experiences with particular encounters. Yes, each Ragnarok is unique and you need to adapt to each fight's particular mechanics. But you shouldn't lose sight of the general mechanics that underlie all encounters. What didn't work for one Ragnarok may work for others. I can sit here and explain to you what went wrong for you in each fight, but that's not really important right now.


Keep in mind that many of the people posting in this topic are veterans with extensive experience clearing Ragnaroks, some specializing in Dark teams. When you have multiple veterans independently arriving at the same conclusion, it's unlikely they're flat-out wrong. My tools are helpful for exploring game mechanics and optimizing your team (if you take all the relevant factors into account!), but they probably won't help you prove that veterans are fundamentally misunderstanding game mechanics. More likely, you're failing to account for an important factor or you're misinterpreting the output.