In older 0ad Versions Civilisations had more differentiations. Then some releases ago there was done a lot of work to make them more balanced. I think there were reasons for that. Altough I am happy that in the two latest realeases there were new differentiations to make the game more interesting. At the moment I rate Athenians highest especially in no Champ-Cav-Games.  Although in early game phase I think gauls is strongest. If you manage to boom in late game I think Mauaries are underrated.  But if you have to fight an army of 50 elephants mele and ranged..... I think there should be limitations for that heavy units. When you face 20 rams or catapults its also gg, at least if there is a minimum companion army on their side.  Maybe you are able to smash the first fiew of them but then everything gets wiped out. Persians and Han can are also very strong if you manage to built a large cavallery.

@Sebastian.ramirez

Personally I prefer not presuming the etymology of those tribal names. It is easier to interpret the personal names as a reference to their tribes. 

Empire phase could be called this https://en.wiktionary.org/wiki/Reconstruction:Proto-Germanic/rīkiją Interesting post from Imperator: Rome forums:  https://forum.paradoxplaza.com/forum/threads/furor-teutonicus-archaeology-and-tribes-of-the-ancient-germanics.1161206/

https://www.researchgate.net/publication/347859019_Cimbri_and_Teutoni this article proposes an interesting etymology for the name of those tribes. I'm not sure it's really a composite word (Sometimes the source mention just Cimbri or just Teutones); but the kumƀrii̯a etymology might be plausible.         https://en.wiktionary.org/wiki/Reconstruction:Proto-Germanic/lugiz It's the word for lie, although probably coincidence (i think name of the lugii might be celtic in origin).