Hard dungeons that I find to be exceedigly difficult

The Labyrinth - finding Rex early is a death sentence so exploration is tricky. Good leveling opportunities are rare since high level enemies are usually along the outer walls (I frequently reach end-game with no popcorn because that stuff needs to be killed early just to level). Often the map creates one long hallway that gives you a (in most cases) 50/50 chance per kill of getting stuck in it once Rex is following. Getting stuck between Rex and a high level mob is usually a game over due to death or critical resource loss. Rex basically becomes Bleaty at half hp; will one-shot kill anything but extreme HP / resist builds.
Shifting Passages - a bit of the same problem as The Labyrinth, only with a much more lenient early game. Frequent losses due to inability to chase the boss through the thin corridors late-game. This can either be easy (strong low-level character starting the boss fight with only a few kills) or extremely hard (many high level enemies remaining with most of the map cleared).
Cursed Oasis - may be more forgiving since the last update, but was probably my most hated dungeon before that. I cannot say what is most aggravating about this dungeon.. the difficult mobs (animated armors, thralls and shades), the excessive curses or annoying bosses. Probably tied with Shifting Passages as the Hard dungeon I'd least like to play currently.
Looking for: Nerfs and/or sympathy and/or strategies to consistently beat any of the above with any class (I try to take in a class I have not completed the dungeon with when one comes up as the burning dungeon).
Shifting Passages - a bit of the same problem as The Labyrinth, only with a much more lenient early game. Frequent losses due to inability to chase the boss through the thin corridors late-game. This can either be easy (strong low-level character starting the boss fight with only a few kills) or extremely hard (many high level enemies remaining with most of the map cleared).
Cursed Oasis - may be more forgiving since the last update, but was probably my most hated dungeon before that. I cannot say what is most aggravating about this dungeon.. the difficult mobs (animated armors, thralls and shades), the excessive curses or annoying bosses. Probably tied with Shifting Passages as the Hard dungeon I'd least like to play currently.
Looking for: Nerfs and/or sympathy and/or strategies to consistently beat any of the above with any class (I try to take in a class I have not completed the dungeon with when one comes up as the burning dungeon).