@Aezeal: I don't have exact numbers, but I play in a CBM EA MP game (Magellan) as Pan, and I have had CW up for a few turns. I hold only three forest provinces (all with temple), one of them has a very low dominion (due to being next to another players capital, even tough it is next to my capital too). Seems the ratio for "good" manikin is one in ten ("good" in my book being the cavalry types, centaurs, elephants; the centaurs and elephants are super-rare, I've had in ten turns two elephants and three centaurs in total), and I seem to generate on average one manikin per candle (plus/minus a few).
It is not a way to instant victory, but they are free, and even the chaff manikin are dangerous to SC's. My manikin (together with centaurs) did kill a gorgon, so they are a nice way to stop SC pretenders in early game (first turn the harpies kamikaze, then the centaurs crash in, and finally the manikin slowly close in for the kill). Manikin are also very nice vs cavalry. However, vs normal troops they are not that wonderful (but then again Pan has minotaurs to stampede through normal size troops; it is just to have the correct troops present at correct battles :P).
In all, I feel CW is more important early in a game (manikin are great vs the usual rushers, and the extra gem-income is invaluable early on but later it is peanuts). In my opinion later on CW lose much of its relative power, and is most useful for Pan to take down some evil hostile global (well, it is random if you get down which you want, but when there are just good globals up, you will always hit something
). Then again, if you can have it up for 50 turns, you are bound to have a nice force of centaur manikin and the elephant manikin, and they would be great even during the later phases of the game.