miss simone, am i being casually racist by having quite a few of the main characters in my planned fantasy series Caucasian (or the equivalent thereof), including the main character (at least, some of the incarnations of them; it's a legacy sort of series

I can’t answer this question without knowing the material. I can’t necessarily answer this question even if I DID know the material.

But I have to wonder what possible justification anyone could have for making fantasy stories in this day and age with a vastly white-centric cast. I would want to ask WHY someone would want to tell a story, a fantasy story where rules are made up in the first place, with no or very little POC or lgbtq representation, in 2013.

I don’t get it.

It sounds kind of like you are asking for someone’s blessing here, but my natural inclination is to ask why you chose to go this route.