Re: How many countries have you played?
 

I played a lot of different races in mp, so i might have forgotten some in my list:

EA: Arco, Abysia, Kailasa, Lanka
MA: Arco, Pythium, Man, Tien Chi, Machaka, Pangaea, Bandar Log, R'lyeh
LA: Arco, Jomon, Ctis

I dont play SP anymore, as the AI is a boring opponent, but before i start an MP game, i test my Nation with different gods and expansion plans.

Re: How many countries have you played?
 

I don't really play dom3 single player, except as test games which usually end pretty early, so I don't know if that counts. Obviously I've at-least tested a pretender build or two for every nation.

I may have gotten some ages confused, but I believe I have played the following nations MP at least once in dom3:
EA Arcos, Ermor, Sauromatia, T'ien Ch'i, Mictlan, Abysia, Caelum, C'tis, Agartha, Helheim, Niefelheim, Kailasa, R'lyeh.
MA Ermor, Pythium, Man, Marignon, Mictlan, T'ien Ch'i, Machaka, Agartha, Abysia, Pangaea, Jotunheim, Bandar Log, Atlantis.
LA Arcos, Man, Marignon, Mictlan, T'ien Ch'i, Utgard, Atlantis.

Did I play Vanheim in MP once? I think I did but now I'm not sure.
I also played a MP game as Haida Gwaii (custom nation.)