Honestly, I think the problem with the Trill is that they just didn't try. It's not like there isn't plenty of possibility there with a minimum of effort (hell, the DS9 Relaunch made the skeletons in the closet of Trill society a running plot thread for 6 books), it's that they were more interested in exploring Cardsassians, Bajorans, Ferengi, and Klingons. Which is fair enough and I can't blame them (well... the Ferengi...), but the Trill in general end up getting the Jake treatment.
I've always liked Playing God well enough, but it was never all that great to me. The backstory was more interesting than the actual plot, unfortunately.