Vampire is a template. They remain dwarves.
Not necessarily. Dwarves had enough belief in "the law must be obeyed to the letter" than they made a god out of the concept. While individuals can serve as a focus, the gods have been made out to be mostly made out of ideas. And Dvalin is the recycling of a dead mortal that most closely stuck to this idea.
I'm not sure which analogy of mine doesn't work, but neither does yours. As I said, there are no RL equivalent to this. I don't believe the power to declare war rests with the minister of foreign affairs in any country. That's kind of a pretty big power to delegate to such a person. But in any case, even if we go with the hypothetical scenario in which the minister of foreign affairs has the authority to declare war (or not), then this in itself makes the analogy improper, because the distinction is that Dvalin presumably does *not* have the authority to.
Seriously. The council had a ton of rules to help protect them. But, *gasp*, they didn't foresee vampiric domination. How implausible is it that a rule-heavy system might contain a few loopholes to exploit? Not the least, in my book...
Vampires are really rare, goodsmoots are maybe rare, and votes on the destruction of the world are probably super rare. So, the opportunities the elders had to hash this out are... probably "never before". That council is also said to not very very representative of the dwarves anymore, it's an ancient institutions held by a bunch of senile aristocrats.
Furthermore, the intelligence of the elders is not a crucial plot point, because more than half of them were dominated anyways. How smart the rest of them are is pretty irrelevant. Durkon's solution is really "thinking outside the box", also self-sacrificing, I don't think it implausible that none of the other elders would have considered breaking the table. As for Dvalin, he's just a rubber stamper.
Is it so super clear cut, though? We the readers get swirly eyes. In-game, dominated people aren't so obvious, you need to roll a check to notice it as far as I remember. The lack of caution on the council's part is not the smartest move, but the abundance of people out there eating tide pods or drinking bath water or bleach is making me not mind as much anymore for characters making dumb decisions in fantasy stories.