I think the new nations benefit from the power inflation phenomenon (I just invented that term
seen in all gaming.
take AD&D, for instance, when it was first released it had a basic lineup of stuff. Soon the devs were releasing more and more material that tends to be a little more powerful than the original stuff. Handbooks with specialized classes, spells, equipment, and all that stuff. Things that cater to the interests that arose in the fanbase.
I think the newer stuff in dom3 follows the same pattern. it seems a little more specialized, and capitalizes on the meta-game and playstyles present in the community; with the game having been around for some time this kind of knowledge became available to the devs, and it influenced they way they created the newer nations.