[Taqwus]

Dominion pushing is also easier if you have a high base dominion.

Priests will help somewhat, but not as much as temples; a priest can only increase dominion in the province that he's preaching while a temple can spread it to neighbors.

Demo is Early Era, right? So you've got Niefel Jarls -- maybe some Jarls with water-breathing equipment backed by Icthyids or Shamblers might work; run around smashing temples if the force is too small to hold ground.