there are too many four-way borders: these are places where four regions meet at a point, for example AP2, AI4, CRC and CR4, so that it's unclear whether the regions on opposite side can assault each other. adjust these so that only three regions border at any intersection.
if the eight bonus zones are meant to represent the eight tribes, then why does each chief not live in his home area instead of elsewhere? the chiefs ought to start neutral (2 neutrals each) because of their importance to bonuses.
try making a bow-and-arrrow different from a tomahawk, for example the bow-and-arrow bonus might be +2 for each chief held.
in the legend, instead of tribe/region
, call the bonus zones tribal domains
or something similar that matches the theme.