What's the best strategy to defeat Haven Campaign 1st mission - 'Something is Rotten'?

Capture the fort and the mines in your area, then try to go east and north to complete the Griffin Quest. Once you have a sufficient army, attack the Lake Orcs and do not stop until you have captured their town, as defeated heroes respawn with the same army here. Convert the area and build up forces to attack the River Orcs. The gates to Djordje will open up, but he only has 2 or 3 heroes that that try to attack you, and once you've taken all his other towns, you can find a large friendly stack of Marksman that will always join you. This should give you the edge you need to defeat Djordje.