I have astigmatism and have the same experience with a lower brightness making it better, not fixing it but better. I have also seen big differences with quality level, my Aimpoint PRO has just a little comma while my vortex is three big fuzzballs together, glass quality must matter, don't own one but tried out a Holosun at the LGS and it was in the range of the Aimpoint on clarity for me. I did not have luck with Eotech, seemed to go in and out for me, good for the first few seconds then my focus goes in and out, nobody has explained this to me as they are supposed to work with astigmatism. I still use red dots on a few weapons but a 1x prism scope has been working better for me on things that would use a red dot.