Weirdly the best ace fic I read in SPN was about Dean being ace instead of Cas. It was a really interesting take on the thing, but not one I necessarily see validated in canon. (I should try to dig that one up again)

Castiel I feel like is a hard character to get right. When he's written well, it's stunning. I've always seen him as a little clueless, but incredibly headstrong. I've back out of a few fics because of the characterizations too but I don't read much SPN anymore as I'm currently consuming the entirety of SGA.

It should be really interesting to see what to happens to Cas in cannon when he's stripped of mojo for real.