I hear what you're saying about the inconsistent documentation - it can be frustrating. This game doesn't appear to have been made with casual gamers in mind. The audience that the Illwinter guys seem to have been designing for is the modern day monk acolyte (ie. the math major, or the coder, or detail oriented minutiae researcher). If spending untold hours researching in a library and then searching all over Europe to find the correct 9 plates to open The 9th Gate a la Johnny Depp in that Polanski film is not your thing, you may find that you never become awesome at Dominions.
For what it's worth, I'm fairly certain that I will never become awesome at Dominions, but in my case it doesn't matter - I enjoy playing it anyway.
I think that's key. You have to enjoy playing it when things don't go your way (and you have to abandon your carefully prepared strategy and suddenly adapt). You have to enjoy playing when you're being crushed by that player who is obviously more experienced (maybe you can learn something from how he's destroying you). Playing when you were foolish enough to take Misfortune 3 and get turn after turn of bad events on your capital in the first year (Misfortune is Misfortunate!).
For me it comes to down to the cackle-worthy moments. When I first started sending mages out with my armies in SP games, the evocation school generated it's share of cackle-worthy moments for me. I just couldn't get enough of blowing away AI chaff armies. The first time I successfully made a thug was a cackle-worthy moment. But even in a game that isn't going your way you can have these little moments when you make things much more difficult than necessary for whoever is stomping you. They've already won. You're going down in flames. But you make it take them 3 more turns than it should have. This causes cackling.
Sometimes, the game seems to be cackling at me rather than the reverse, but I enjoy those moments too. So many of the random events and even some of the heroic traits (Heroic Obesity?! Ugh!) seem to have been added to the game when the Illwinter guys were in a particularly puckish mood. I can just see them cackling over this stuff as they coded it in. So many spells in this game are evil! And the items! Eye of the void isn't even all that bad, but when I first encountered it I wouldn't go near it. Replace the commanders eye? Gives an affliction and a chance for a horror mark?! Sure, this item has it's uses, but the entire game is riddled with stuff (traps!) that may or may not be useful in certain niche situations. Playing this game is like being Indiana Jones in an ancient temple full of traps. There are goodies that are definitely worth it, but there are also spiders dropping on your head. And spikes coming up from below. And a cute little old lady offering you chocolate mouse* and the opportunity to play host to something unholy.
This is a really involved game - it's also evil. It doesn't fully reveal itself to the casual player, and you may never know all of it. But that means there's always more to it, and that's what's great about it. Not everyone is going to feel that way, though.
*"As long as she ate the mouse, she can't see nor hear. Now sing."
http://www.imdb.com/character/ch0010586/quotes