High PD kinda useless.

[NTJedi]

Graeme Dice said:
Beyond 20, you are throwing gold away on immobile troops that cost more than their equivalent mobile versions.

Well that depends on the situation. Mobile troops use food supplies, can pickup afflictions, die permanently and the more mobile troops purchased the greater their gold upkeep.
The units from province defense don't need food supplies, won't die permanently and have no gold upkeep.

Graeme Dice said:It wasn't the province defense that allowed you to defeat your enemies, it was the flaming arrows from 100 longbows.

I agree... the flaming arrows from 100 longbows definitely was the reason for holding the province.