Been playing a week, mostly berzerkers. Here's the order of dungeons that appears to be the "normal" way to go, at least for my zerkers:

Trollmire, KorPul, Norgos, Gloom, Maze, Old Forest, Rhaloren Camp, Crystal Cave, Sandqueen, Daikara, Golem Graveyard, Ruined, Hidden, Halfling, Elven, (Spellblaze?), Dreadfell

For the freeing of Derth, any time after Daikara when you have significant Lightning resist. A good strategy for me seems to be to fire the RoR as soon as I enter, burn off about 20 rounds, then head in, circling the perimeter, and Rush the first elemental seen, and fight just one or a few before getting yanked out. That way I can whittle them down without getting swarmed and burned to a crisp.

Lake Nur is odd - obviously better to get early, say, after Daikara, but sometimes it's just too hard, what with Luminous/Radiant Horrors and Headless Horrors. Then I usually die, confused and alone, and put if off for later.

The Graveyard East of Last Hope I've learned is even harder than Dreadfell. Eternal Bone Giants hose me no matter how well I prepare. I've only killed one, I think.

I'm told Spellblaze is much easier than Dreadfell - I always assumed it was the "last" dungeon. Need to find where in the order it should go.