i think one of the things that makes damage kind of hard in this game is the connection between dealing and taking damage as well as the nature of taking damage when compared to DnD.
this example is taken from our game, we are level three so the numbers reflect that. the scaling could change at higher levels but i can only foresee the divide growing wider, not smaller.
in DW the lower hit die of some classes (mainly thf but bard as well) make it difficult for them to actually engage in melee combat. at level three, the thief in our group has 15hp and wears mid tier armor (soaks 2) compared to my fighter who has 36hp and wears top tier armor (soaks 3). the expectation of taking damage to do damage allows for a fighter to stand up in a melee because he has the HP to shed to keep fighting while the thf can stand maybe 2 rounds before they need to heal.
this also holds true for dealing damage. while there is not really any difference between the base damage we can do (thf can get the ability to use the largest weapons and poison is comparable to any of the + damage abilities that a fighter can get [the only real difference i can see in base damage is the ability for the fighter to take dual wield out of the ranger tree while the thf cannot]) the real ability to do damage is the option to double damage in exchange for taking a hit if your roll 10+. this allows the fighter to take some damage which he can tolerate to do a lot of damage while the thf cannot take that damage as casually.
i am not saying that all classes should be equals in combat, but already at 3rd level (and even at 2nd level) in our game my fighter was doing 80% to 90% of the damage in combats in a group with a thf a bard and a wizard (who doesnt really count, all he could do was cure light wounds...) both the thief and the bard were using d8 bows because they would not have been able to survive getting into combat. when they did they tended to defend my fighter almost constantly to prevent themselves from just dying.
again, im not sure of a good fix for this, and i have no idea on what youve already worked out for your revamped damage system. these are just some observations i have had.
oh, a few questions:
*when choosing to do double damage for melee or empowered spell would you say you have to choose before rolling damage or wait until after. (we've been playing choose before and will probably continue that way no matter your answer, im just curious.)
*same thing with adventuring gear. state youre using it before the roll, or wait to see if it is needed?
*with the defend move, perhaps remove the ability to spends a hold to move damage from yourself to the person you are defending? this would make the meatier types (pals and fgts) need to look out for their squishy comrades instead of making the softies spend all their turns defending the tanks so they can divert damage to the guys who can stand it. just an idea...