Questions about PD and other

[Archonsod]

Sombre said:
60 PD may be technically inefficient and a bad move

It's not always a bad idea though, PD has it's own advantages that a normal army doesn't. For example, it's unaffected by sites which spread disease, thus if you're unlucky enough to find Inkwell End or similar in a key chokepoint then it's cheaper in the longterm to invest in high PD rather than constantly be replacing defenders, especially if you're a resource heavy nation.