[thejeff]

Except, the stealth/strong priests, special pretenders and cheap temples aren't enough to do the job. Those special features can help defend against a dominion push and you may be able to leverage them to finish off a low-dominion nation or squeeze dominion out of a last for that you can't take by force, but full-fledged domkill really needs blood sacrifice.
Having higher level priests available helps with sacrifice as do cheap temples, but easy access to Jade Knives and good bloodhunters helps more. Stealth is largely irrelevant, since you can't sacrifice and hide.

As for these being hidden balance features, I don't really see much correspondence between "weak nation" and good at dompush or "strong" and vulnerable.