What mods (submods) do you play with and why?
I've enjoyed cultural tensio (not certain if it's working with the current DeI version?) and De Ai Arbitirs. Also using the No HDR mod, as it really helps with the terrible shadows.
Also really wanted to try Data Venia, however it's usually not up to date.
Music: tyso3's epic music mod is fantastic.
EDIT:
I forgot to mention another mod I am using that REALLY adds to the battles. It's the enhanced particles mod or something along those lines. There's virtually no dust in vanilla Rome II, this makes it quite a bit more realistic.
Also if able could you provide a link to the mod you mention?