The damage caused by your entire army can be undone with a few courtiers. 
That's not really true considering in about a week I know of a region that had lost 3k peasants limiting its production considerably for quite sometime. Also the "if you can loot all the regions why not take the capital, I know of one example where they couldn't take the the capital but could loot the rest the regions. Carelia's army could not defeat the Suville army looting it but Suville couldn't attack the capital because with the long time militia Suville's army would outmatched.
