What's the best weapon the group has? I thought something (the Fire elemental, IIRC) had +3 DR. Without a single class caster, I don't think GMW is an option - courtesy of that spell and a Bead of Karma, some of our fighters were running around with +4 weapons.
Having a cohort should help quite a bit. I wouldn't exactly use my group's experience as the best guide. Because of the tight confines of many dungeon rooms and corridors, we often couldn't use our numbers effectively. Also, some of the characters were less than effective - like a sorceress who started with a 14 CHA. Also, we didn't use the best approach in many cases - for example, that Slay Living riddle trap ended up hitting every single character. And my character made it through the entire adventure without dying.
We actually didn't have too much trouble with the mooncalf. While it was one of the few times I had to heal someone in combat, our dwarf paladin managed to hold its attention by "letting" it grapple him.