Let me start with the good news here. The original versions of Dungeon Lords had bugs in them that could prevent you from completing the game. In the original Dungeon Lords, sometimes the gate leading out of the starting city wouldn't open, preventing you from seeing about 90% of the game, and even in the CE, the Shadow Ruins were broken, and if you left that area before collecting the Relic of Power, then there wasn't any way to get back inside, and your game was broken. As far as I'm aware, no bugs like that exist in MMXII. The MMXII bugs are just irritations.
So what's currently wrong? None of the skills or spells have descriptions, making it difficult to tell what they do. Weapons along with armor can be damaged, but weapons lose durability so fast that there isn't any way to keep them repaired (there's a repair skill, but for some reason repair kits are rare drops, and so the skill is almost worthless). Once you pick up a Crystal of Life (which happens early in the game) death no longer has a penalty. There isn't any way to advance time, so sometimes you're forced to explore in the dark. It's possible for high level characters to lose the ability to learn new spells. The game is sloppy with quest items, and you can lose half of your inventory space to them. The game automatically decides whether you should use a ranged or melee weapon, but this process is a disaster, and it probably means you won't equip a ranged weapon. The manual wasn't updated properly, and half of its information refers to the original game and is no longer relevant.