Maynid is right, it's simply a question of card pool. Any Gold defense is going to use Wonders Forgotten and Failed Objective, so if you see a lot of Gold characters you know they're in there. Where the differences come in are more on the fringe and individual flavor. For example, Besieging the City is not found in many decks, despite being one of the best Evil Enhancements out there. It's just not popular. Likewise, many people swear by the entirely over-rated Chariot of Fire, when in fact it should only be used in certain decks.
There is a lot of similarity among top decks, but--especially with the new Dom Cap--there is usually a variance of at least five cards, often more, within even very rigid deck types.