The indie game Knights of the Chalice is a very good dungeon crawler. The turn based party combat is challenging, because the enemy artificial intelligence is much better compared to many high budget games.
This game is NOT about story or party interaction it is about C.O.M.B.A.T..
The balance of the game is good except for crafting, you can craft nearly anything on higher levels with gold and XP-points, only.

Buy this one, because I want more of these games :-)