I always understood that serif fonts were easier than sans serif as (especially for those like me who have astigmatism) the serif guides the eye more easily.

And I tend to agree.
But.. I think you have the font size set too small; it does not render terribly clearly on my screen, which I think is why others have complained it is harder to read.
Without checking, I'm guessing it's 10 point - accessibility recommendations usually call for 12 point for real clarity. Is it worth trying that?