Recommended difficulty level is "Warrior". This will provide reasonable neutral creatures, a more or less sufficient amount of resources, and a fairly intelligent AI.

I'm playing as a Warlock on the Hero difficulty, and IMHO, the neutral creatures are quite manageable (they can be defeated in one or two turns). Within the first three weeks (23 days), I eliminated the demons, and now everything depends on how quickly I can find a path to the top and eliminate the other players. I don't think anyone will be able to offer significant resistance to a plague-spreading nuisance of level 25 with a spellcasting level of 32, because the humans, barbarians, and dwarves don't have undead or mechanical units. I'll try to get out of week 7.