When the dark matter sails through, is there still enough mass to keep it together, or do they evaporate? Are there "dark galaxies" to match the dark-matter-less ones?

I can't imagine how we'd ever find them. We'd have to get extremely lucky and find one that happened to lens another one behind it. That happens rarely enough with regular galaxies, and I imagine that those "dark galaxies" would be even rarer.

(And you'd still have to consider other explanations, like black holes.)