However, straw burns- and mildews, rather easily. I'm sure they have ways to minimize the negative consequences of this, but I think the dirt houses may be easier?

What do they use for roofing on the Eco-Domes?

Actually, straw bales burn very poorly. When locked away behind a layer of stucco, even more poorly.

Ditto for mildew.

The earthquake resistance, pest resistance, and insulating qualities of straw bale construction are mind-blowing.

Okay, I can agree with a tightly bailed bail of hay not burning (as long as it stays tight) but mildew? I've seen a lot of mildewed hay in my life. Living in a farming community, I know the importance of keeping your hay dry. Of course, I'm not totally familiar with the construction techniques- if you have any links you'd recommend, I'd be willing to read up on it.