I need to make a slight alteration:
Construct Factory is actually ranked second, with Fire temple third. It was the first dungeon I did (by accident) and therefore it was a long time ago since I played it. Due to it being early game I also couldn't get the hang of the mech and found it...
It's cool to see others who enjoyed these dungeons. I agree that they still have some ways to go before they've truly perfected the open air dungeon formula, but these are a lot better than many give them credit for.
If I were to follow your definitions of what the dungeons were then my ranking is the following:
Forgotten foundation: I personally wouldn't have counted this as a dungeon but I'll include it regardless. It's a neat gauntlet before the final encounter and does its job. The final moments of...