I have never won a sp game...

[Agrajag]

IIRC, higher starting dominion increases the chance for each temple-check to succeed, so a high dominion is useful for those without priests.
You need to remember, though, that dominion has to "fill up" before it can spread further, so a higher dominion score also means it will take your dominion longer to spread further.

Atleast, that's what I remember from all the previous "how does dominion work?" threads...