clarification on damage formula for weapon attacks

[Kyubi Xiaolong]

as the title says i think i figured out a rough draft of the damage formula for weapon attacks (basic attack and powers that say weapon attack)

((X+Y)R) - Z

X = total of all weapon damage types after taking into account resistance, immunity and weakness to damage type

Y = apporpriet attack power stat (attack power, spell power, sexiness)

R = random variable

Z = apporpriete defense (armor/ward/focus) divided by 2% (this is based on fact hovering your mouse over then they show that 50% of the stat is the % reduction to the type of damage it resists (physical - armor, magic - ward, tease - focus)

am i warm, cold, close?

 

[Prince Charming]

base_damage * (1 + attack_power / 100) / (1 + max(target_armor - armor_penetration, 0) / 100)
Then process the impact of elemental resistances which are self-explanatory.
There's also a small randomizer effect as you have noticed, it's +/- 5% if memory serves right.
I would show you the proof but it'd be quite painful to gather the gibberish of post-minified javascript that you can retrieve from the developer console. If you're really interested in the proof I'll pull that up next time I'm on the forum.
Also for what it's worth :

• You're correct in that the enemy resistance depends on the damage type: physical -> armor, magic -> ward, mental/sexual -> focus. Notice however that damage type (physical xor magic xor mental xor sexual) is distinct from elemental type (penetrating, crushing, fire, ice, storm, holy, blight, acid, raw). If your weapon deals some ice damage (eg griefmaker), a basic attack with it will deal ice damage against enemy armor, even if ice sounds like magical damage to some.
• Even more interesting is the penetration stat used: it depends on the tags you can see on the power's card in your codex. [Weapon] powers use armor penetration, [Spell] powers use spell penetration, [Tease] powers use temptation; all other tags are irrelevant to which penetration is employed; if two or more of the relevant tags are there, then only the highest penetration stat is used; if none of the relevant tags appear, then your Strength score is used as penetration.
• That means that a [Weapon] power which deals damage of the magical type (Arcane Shot comes to mind) will use your armor penetration (due to the [Weapon] tag) against your target's ward (due to the magical damage type).
• The basic attack is actually a [Weapon] power just like shadow strike, shell cracker etc...
• Crits add 100 + 3 * Cunning to the "damage power" used, eg a basic attack crit pre-mitigation damage is base_damage * (1 + (attack_power + 100 + 3 * Cunning) / 100)
• As of the current build, sexiness is counted as a "3/4 damage power", ie tease pre-mitigation damage is base_tease_damage * (1 + .75 * sexiness / 100). base_tease_damage is 30, and there's also likes / dislikes factor that give some marginal +10% damage or something in this particular case. This .75 factor, sexiness being capped at 100, and sexiness also counting as bonus accuracy for [Tease] powers may or may not change in future builds.