Congratulations! good to know you finally got something that looks reasonably good, though you should be able to achieve this without adding a minidsp. Since you are using the mini to improve LCR, are you using two of them then, as the minidsp 2X4 HD has only 2 analog inputs but of course there are other minidsp models that has more inputs.
Anthem really has good potential but I don't think they would invest more time/funds on making it more tweakable because the vast majority of their users (you obvious know as you have visited AVSF haha) are happy with ARCG and many thought it's much better than Audyssey and Dirac Live and very few of them would bother checking measured results with REW.
With the miniDSP, you should be able to do better in the 20-60 Hz yet but of course only if you are ocd like me... Even without the mini, again, it could be done but it would a trial an error process that may last for hours just to gain 2-3 dB of smoothness in that deep bass range, imo not worth it at all, but with the mini it probably would take less than a few hours to achieve better looking curves, though again it might sound that much different audibly, for real world use.
I have never seen anyone posted better looking curves than you have now, mine look a little better in the 20-60 Hz range but not better overall, and it obviously is hard to compare and draw any conclusion as it is not apples to apples. I do feel comfortable to say for those who is keen on measurements, they might be happier to go with Audyssy and/or Dirac Live capable devices because with ARCG, pretty looking curves (say within +/2 or even 4 to 5 dB 1/12 smoothing) just don't seem possible as you and I have found out.