[Maksimum_Fire]

I think you missed my comment earlier. I don't think Dagger Dance should just get the massive damage amplification from Ether Invitation or the FP sapping strength of Ritual Sword. It can just stay as an extra 20% basic attack damage every the skill, without those skill effects.

And while you comment on Fleur while dualwielding weapons, you're not addressing the fact that Fleur allows you to simply use one weapon and benefit from full swing. 20 SWA is a sizable increase to not only basic attacks, but to autohits, as well. Twin dance struggles with damage in any sort of traditional setup because of this, and already pigeonholes itself away from autohits(or at least, from getting any real damage out of autohits).

Fleur trades a small amount of damage after basic attacks for much more build flexibility- which can be tanky stats and damage reflection(Mirror shield/guard with Shields), damage matching or beyond what dagger dance achieves with potentially better utility(2hand and glove, which also gives bonus hit) or the ability to perform combos that aren't possible without it- combos that require 10m or more, like you mentioned. Fleur is infinitely more versatile, and outshines twin dance for the plain and simple reason that it's much easier to use, more reliable, and doesn't force you into specific options. And even in optios that Twin Dance can shine in, Fleur can often shine just as well in- especially with the minimal support that twin dance has.

Remember to read the previous posts; I'm not suggesting that all effects are duplicated. I'm suggesting Twin Dance work as it does now, and just function as a bonus, 20% damage basic attack after basic attacking skills. I don't think that's unreasonable, it just makes the flow of combat for dualwielders more intuitive.