[Lazy_Perfectionist]

Speaking from a tactical perspective, there's no difference between dominion 3 and dominion 8. Excepting only pretenders, prophets, and certain nation(s) such as Agartha, Golem Cult or R'lyeh for the spawn.

Scales will shift faster with higher dominion (as result of more temples leading to greater max and spread), and be harder for the enemy to counter, yes.

Having your dominion in hostile territory (even w/o scales) will rob that nation of any positive effects from the scales. It can also perma kill gods and combo with certain spells.

Those factors are not too minor- but can often be achieved other ways, i.e. through temperature-changing spells or simply by maintaining a defensive stance and letting the enemy come to you. This means that just enough temples are a good idea, and a temple boom/dominion push needs to have a specific objective in mind, and defensive plans in place. It's not like economics, where its always a good idea. Go for balance, then skew to one direction once you're planning a war.