...and that's what I'm hopefully going to prove wrong.
I'm telling you, the numbers say that Mictlan is the best possible late game Dominion spreader, bar-none. With the capability of having at least 3 temples per province (more with a better economy and magic items, but I'm trying to be conservative), I think it's just waiting to be discovered. It's funny; when I first read about Mictlan after buying this game a good while ago, I immediately thought, "Wow, the purpose of this Nation is purely for spreading Dominion." I was very surprised to see that everyone's strategy with them had nothing to do with Dominion killing.
Of course, the difficult part is making it to that late game in a position where you can win.
=$=
PS -- According to the Dominion Spreading Bible, the prophet does not spread Dominion for Mictlan. He'd have to make sacrifices, too. My guess is that Juggs don't, either.