High PD kinda useless.

[Graeme Dice]

Forrest said:
Over 1000 troops and two Gods died trying to take that province. I held with minimal reinforcements and just a three or four spell casters. That 40 PD was the best spent money of the game.

Except that it wasn't. There's little point in raising defense beyond the point where it costs more per additional troop than those troops would cost you to buy in the first place, and that breakpoint is around 20 for most nations. Beyond 20, you are throwing gold away on immobile troops that cost more than their equivalent mobile versions. It wasn't the province defense that allowed you to defeat your enemies, it was the flaming arrows from 100 longbows.