[MaxWilson]

...being in enemy dominion causes unrest?

I had forgotten about this until recently. So the reasons you want a good Dominion score:

1.) It helps your pretender/immortal units.
2.) It gives a net +2 morale boost to your normal units.
3.) If you have good scales you need to push your dominion to benefit.
4.) Even if you don't you need to push your dominion to keep taxes at 100.
5.) Spells like Gift of Health, Lure of the Deep, etc., rely on it.

-Max