I agree with MerricB, and have had similar experiences (though I have not played this dungeon).
The 5ft hallways are boring in a party with several melee combatants. Some of you have suggested tactics which MerricB have proven to not work at low levels (tumbling, high level spells).
Others have mentioned withdrawing to an advantageous position. While this is a possible tactic, the iniative system discourages this as essentially it causes the group to act on the iniative of the slowest person in the group. Also, it is really bad if everyone flees but the last person is overtaken by the monster (grappled, dying, etc). Moreover, in MerricB's example, the monster would get a "free" attack in an attack of opportunity on the PC in the small room when he withdraws.
In the end a withdrawal might not cause the monster to blindly follow them anyway, and rather withdraw to a strategic position itself, or worse, alert the rest of the dungeon inhabitants.
As a curiosity, hallways usually wasn't used in medieval dungeons in the first place. And really, a lot of the corridors in the map presented doesn't make sense at all. Why have corridors between two rooms? Corridors were invented so that you didn't have to enter all rooms to get to the other end of the castle.
In conclusion I think I'm with Hong in avoiding dungeons altogether
