The way I understand it, when using elements of all 3 expansions players must use all crisis cards, destination cards, skill cards, quorum cards, etc together. They can't pick and choose some of these.
But with a crisis deck made up of the cards from all 3 expansions and the core game, there are very few cylon attack cards. So if you're not using the cylon fleet option from Exodus, chances are you could go a whole game with no cylon attack crisis cards, which makes for a game light on combat.
That may be preferable for humans, but am I doing something wrong? It just feels a little like cheating. If its intended then that's okay. There's always the cylon fleet option if we just feel like more combat.