I used the following build, on hard mode, with permadeath: SwiftStriker Bushido QiGong Master Of Arms Shield Bearer Berserker Rage Killer Vegan It was kinda funny, I nearly got myself killed, managed to retreat behind a door, and while I was healing up, dredmor managed to... kill... HIMSELF, at half HP, in the other room. Kinda anti-climactic.
Dredmor has an odd tendency to suicide if you can escape him after your first encounter. Not sure what prompts this, if its a bug or if he just has a bad habit of flinging spells like fire glyphs around then get caught in them. Arch Diggle has recommended therapy with the Diggle God of Fertility, but I think he should just lay off the Emomancy...
Not exactly what I meant to say. Actually, in my experience Dredmor is pretty easy if you can get to him, but sometimes he does seem to die under... mysterious circumstances. The first time I killed him I hit him with the Recursive Curse twice and teleported to safety. He died four or five turns later. Did I earn that victory? I sure think so. But if you ever wonder what Dredmor is doing off by himself... Well, it may be better not to ask.
What can we say, you ran away from him resulting in no lemon, so he died from scurvy. But in all seriousness (as the above one is just a lame joke, which you probably had no trouble noticing), it's not an empty victory. It's your first victory ever, and thus it gives you knowledge about what to expect on your road to Dredmor. Sure, it is a little bit anti-climatic that he killed himself, but that is going to be fixed sometime, and then you'll have it much easier to get to him once again, because you were there already, and you know what to do. Other than that, well, Dredmor isn't really difficult either way, as most builds are optimised for 1v1 fights either way, which is why we are using chokepoints when stumbling upon monster zoos, and individually (after you take care of all the other mobs) he's comparable with a monster from evil chest.
With the added bonus that he doesn't spawn right next to you, so you have an opportunity to chug potions/lob bombs ect if you wish.