[Vicious Love]

Both Jotunheim and Mictlan have easy access Crossbreeding, which benefits from luck. Jotunheim has some of the best heroes in the game, while Mictlan's are merely decent. Nothing spectacular, but they give access to additional paths, including the blood/air combo.

T'ien Ch'i's immortals are well worth the luck scale, as are Ermor's heroes, though the latter are kind of hit-and-miss. Which is not to say that Mortius or whatsisface are misses, simply that Etimmu is unquestionably a hit, and can give you a tremendous edge in the early game.

R'lyeh require a luck scale. If you don't get Cthugul, you'll need either the Gift of Health, the Chalice, or a bunch of water breathing faerie queens or priestesses just to support your perenially feebleminded void summoners, and you still won't summon particularly effectively. Besides, the other two heroes are pretty sweet, as well, particularly the aboleth.

Man is the only nation with inexhaustible heroes, but they're really nothing to write home about. Beats only getting Ulm's heroes, though.