^^ Nice build. I'll look forward to some parse info.
I did some more testing over the weekend as to the effects of MND on the Flat Blade and Spirits Within combo multipliers.
From what I found is that at 240 MND, you get the 4.5x combo bonus on Flat Blade, and the 1.5x Bonus to Spirits within. There is no difference up to 320 MND. So I imagine that 4.5 and 1.5 is the cap (for lvl 50 anyways)
240 MND is as low as I tested this. Which is 8 pts above my base stats.