Reality is always more strange than fiction.

She didnt get drunk, she was exposed to alcohol!

Is that a good thing though? In your example, making 2 districts of strong group A, and 1 district of strong group B you are encouraging extreme views that dont work well together (basically what we have now). The minority group is always the loser no matter what because 2 beats 1.

If we just went by proportion it could isolate minority groups, but would more than likely foster electing 3 moderate candidates that appeal to the majority of people in the middle and actually accomplish things instead of fighting for opposite goals. In this case minority groups become the swing voters that decide elections so their concerns get amplified and are more likely to be addressed by whatever party is in power.