Considering the vanilla campaign map of Rome 2, I actually think it's quite good, of course that is in comparison with other vanilla Total War campaign maps. It does after all have the most regions of any vanilla campaign map yet. However, CA's campaign maps have never been a paragon of accuracy and detail (though the same also applies to Paradox games aswell), they can't really be compared to what mods have produced.
CA has been saying that they want to support Rome 2 with mod tools similar to those of Shogun 2, and that would mean that the campaign map will likely become moddable. If and when that happens, making an accurate, more detailed map will be one of my primary focuses (that is if having to constantly deal with ignorant forumites

about the current state of modding in the Total War series doesn't drive me away from here first). After all, I am one of a very select few who currently knows how to mod the campaign map on the warscape engine. And perhaps the only one with the current knowledge of how to build a entirely new map from scratch on this engine.
In fact I am currently researching information for a more detailed map. I currently have a concept completely for a map with 77 provinces and 211, and am now working on a more detailed one with around 110 provinces and 300 regions.
Here's a small preview of the map I am working on... rep for the first person who can name the six provinces in the Iberian peninsula and all the cities (or atleast most of them)