How is skill damage calculated based on weapon damage?

To answer the question posed in the initial question: Only if you had 0 intelligence and no other damage bonuses!

Base damage is simply weapon damage + any damage bonus from gear (+elemental damage is effectively "+damage" as far as the system is concerned).

The formula is roughly as follows

Base Damage =
        (weapon damage range + bonus damage from gear)
        × bonus from primary attribute^†
        × other class bonuses from skills.

Ability Damage =
        Base Damage (as above)
        × % Weapon Damage listed on the ability.

^†1 primary attribute = +1% bonus damage

Weapon speed doesn't come into play at all when calculating damage from abilities.

What this means is that weapon speed is balanced as a stat; either you deal more damage per hit (by picking a slower weapon), or you use more abilities (since weapon speed affects animation time). DPS is entirely useless as a comparison metric unless you're only auto-attacking.

I can answer this with my in-game experience now.

Weapon damage is calculated exactly how you would expect:

Scenario 1:

You equip an apprentice's wand: 3.0 Damage Per Second, 2–3 Damage, 1.20 Attacks per Second.

Magic Missile (110% weapon damage) will do 2.2-3.3 damage. You can cast it 1.2 times per second

Scenario 2:

You equip a variation of this wand: 3.0 Damage Per Second, 1-1.5 Damage, 2.40 Attacks per Second.

Magic Missile (110% weapon damage) will do 1.1-1.65 damage. You can cast it 2.4 times times per second

Notice that for spells that cost arcane power, the spell cost is not adjusted, so faster attacking weapons "consume" more arcane power for the same DPS.

Advantages of fast attacking weapons (wands 1.4, daggers 1.5):

• Better for "per hit" or "per critical hit" abilities, such as AP per crit

Advantages of slow attacking weapons (2h maces 0.9, staves 1.0):

• Easier to to find. (even when factoring in the off-hand)
• Consumes less resource
• Better for kiting
• Better for damaging cool-down abilities (for example, wave of force)

Another fact that I found very surprising: The weapon speed changes only the speed of offensive abilities. For example, I can cast 4 teleport with wormhole regardless of my weapon speed. So I thought that fast attacking weapons would give you an advantage for casting defensive spells, but this is not true. The casting speed of defensive and ability spells is always the same.

So it's not a surprise that my build involves a 2handed mace and no signature spell. I am currently running through hell solo and it's very smooth. I expect to end hell with this build without any difficulty whatsoever. (expect for a few very bad-rolled rare packs). Edit: Now I am soloing inferno (i have adjusted my build). The first act is very easy. The only problem are bad rolled rare packs. I have to avoid about a third of them.

I don't this this is explained anywhere, and I haven't heard of anyone doing enough testing to figure it out yet (I certainly haven't). This is something I'd like to know too.

I believe your inclinations are correct: it would cost more Arcane Power to use a higher attack per second wand.

Here's how I suspect it works:

• Faster attack speed makes you attack faster with all abilities
• Higher attack damage makes you hit harder with all abilities
• Two weapons with the same DPS but different attack speeds will cost different amounts of power (Mana/Hatred/Spirit/etc.). There is no adjustment for speed.

In addition, most characters (Monk, Demon Hunter, Barbarian) have power-generating abilities. Attacking faster with those abilities means faster power generation, which would offset the fact that attacking faster with power-spending abilities makes you spend power faster.

I don't have a good source for this, but I am inferring based on my experience, my thoughts on how I would do it if I were designing the game, and the Monk ability Fists of Thunder which specifically states that it is inherently faster and therefore generates more Spirit than other stuff.

The power-generating abilities aside, straight damage values might make it seem like stronger, slower weapons be strictly better because they cost less to put out the same damage as fast weapons. However, damage isn't everything. When you attack slower, it takes you longer to cast each spell. You can't react as quickly, and you might miss more often due to enemies moving around. It's harder to take a swing (or shoot some lightning, or launch a kick) and move afterward. Try out a Barbarian with some giant axe and you'll feel a definite difference.

I have a feeling that mobility is going to be important, especially in harder difficulties. This would mean that being able to poke quickly and change position, or get a bunch of power in a hurry, will be valuable. How valuable it is, though, you'll have to decide for yourself based on your own judgment and playstyle.