I've been thinking about this all night, to the point at which my dreams were of DW (how sad is that?), but the result has been a few ideas :)
First, I really really get the disconnect between player variable damage and monster fixed damage. My first impulse (which I wrote a post about ages ago) was to make PC damage fixed too, like in AW. Sage and Adam said that that was dragging the game away from the roots of 'to-hit & damage' of D&D and I agree.
So, then I thought, perhaps the players could roll the monster's damage when the fiction warranted it? They then held the onus for the damage caused to their character. Do you give them the option of attack fictional move or hard damage each time? Too much rolling? I don't know.
I don't think that the DM is a 'neutral Arbiter' Dan. The rules explain what your role is, its totally on the side of the characters. Dungeon World calls you to act in a particular way as GM for the rules to work at their best. Sure, you are refereeing and adjudicating, but always with your agenda and principles in mind. Dealing damage to the players is a HARD move, one of the hardest you can make and you need to think if that is warranted fictionally (in or out of combat)?
@Nemo: I like your style! And I agree wholeheartedly with your evaluation of AW PCs. I like to relate them to Paragon Tier 4e characters, death being the least of their high-powered concerns. Taking away their stuff on the other hand....
That's a great way to frame the rules for a first session of DW with some folks used to 4e. Awesome! I know that consistency is important, so perhaps the process is consistent? Perhaps with the Death Move you could treat each situation on a case-by-case basis? If the player seems really upset that their character might die, use everything in the RAW to help them. Give them choices. The rules are there to help everyone tell a good story and they are very malleable fictionally. If you like, you can always make up your own rules as a custom move!
'Who has the highest bond with you? How can they help you face death? Tell me what you do.' Or give them an opportunity very much with a cost (which is effectively the death move as is). 'That blow should have killed you, any other mortal would have died, but not you. There is no afterlife, no gods, no death offering bargains, you are just left for dead.'
When you take your last breath but refuse to die, you are in a coma and let for dead. You have 1 HP. Take all the damage you have suffered below zero and divide it among your Stats, subtracting as you see fit. No Stat may go below 3. Adjust your bonuses accordingly. You are scarred, physically and mentally. This is a life changing event for you, when you awake tell us all about it.
@Glitch: I dig what you are doing man, it is a tricky slope! If all the players clamour for the same 'treatment' everytime they face death's door, then my favourite GM move is to disclaim decision making and sometimes let the players decide. 'I don't know? Do think they should die? Or live?'