There's always so much going on in the show, too much I think (especially season 2) and it just doesn't seem to mesh properly, it tends to leave questions unanswered which can be a little unsatisfying. Great cast and production value though.
This has been my main problem with the series as well. It's like the writers come up with a basic premise -- say, a haunted house -- and then throw everything they can think of at the wall and use it whether it sticks or not. What you're left with are multiple hastily executed sub-plots jockeying for position, and the result is a jumbled mess. Especially seasons 2 and 3. In comparison, season 1, which started off sloppily but got better as it went along, seems like master story telling.
Season 2 had more story lines than it could keep track of (the alien abduction sub-plot, which was never resolved, was especially frustrating) and while Season 3 started off strongly (thanks in large part to the powerhouse performances of Jessica Lange, Angela Bassett and Kathy Bates, who all but carried the season) it became quickly apparent that the main premise was actually TOO thin to hang the various sub-plots on. Even more stuff is left unresolved and the final episode is particularly anti-climactic.
The only reasons I've stuck with this show so far are, one, Jessica Lange (she brings class to the show just by being in it, not to mention she's a fantastic actress and still quite a head turn despite being in her 60s) and two, because I honestly do see real potential here. If the writers and show-runner could only settle on and fully explore a primary storyline and allow the sub-plots to organically flow from it, instead of trying to cram everything they can think of into every single episode, this would likely be a show worth celebrating.
Seriously, look at all the sub-plots they've thrown in in just these first three seasons. The show has good ideas, it just doesn't fully explore any of them. You can take just about any sub-plot from these first three seasons and flesh it out into an entire season of its own, instead of what the writers do now, which is pay each sub-plot lip service, then toss it aside for other sub-plots they treat the same way.