Okay, well my barbarians are on the way. But in the mean while I have decided to try a smaller campaign with just the five armies I have already.
I have slightly changed the way I am doing the cards. Each card is labeled "Invasion", "Land Grab", or "Invasion or Land Grab". Each is also labeled for the army it belongs to.
Then as before each army starts with 1 card and for each three hexes they claim they get a bonus card.
When the army has a card drawn it can do whatever action is listed on the card. So a Invasion card allows the army to attack a hex claimed by an enemy army that is touching a hex that they claim. The Land Grab card allows the army to claim any unclaimed hex touching one of their claimed hexes. Then the combo card allows the army to decide which one of these actions they would like to take.
If a card is drawn that the army cannot complete, such as drawing a Invasion card without any enemies to attack, the army does nothing (imagine they are recruiting, resupplying, whatever).
I played out around 7 campaign rounds last night. They resulted in around 4 battles. By the end of the night the dwarves claimed 7 hexes while the most anyone else still held was 5.
I think this system will work well for keeping me entertained for a few weeks. Oh and when a army gets bonus cards for claimed hexes, these are randomly drawn from the master pile. So each army doesn't know if it's getting a Invasion card, Land Grab card, or combo card added. This simulates the politics without needing to go into details.