Like so many other balance complaints, keep it in mind that the balance here is not "chess game" balance but more of a "rock-paper-scissors" balance.
Since there is no effort to make each nation balance to each other nation, grading the balance needs to take into account ALL of the features of a nation. PD is one of those features. Where one nation is weak in magic, another weak in armor, another in support, etc etc then the fact that a nation is strong or weak in PD becomes another thing to consider when you choose a nation which best matches your mode of play (or makes up for your lackings).
You know what the standard response on developer forums is..
Dont think of it as a bug. Think of it as a feature
