Does anyone know how much STR is Equal to one weapon attack?

1 WA or 1 MA = DM*(4 * PS + SS) / 100

Where:

DM = Damage Multiplier of weapon
PS = Primary stat of the class that uses the weapon
SS = Secondary stat of the class that uses the weapon

Note: The Primary Stat is the stat that yields more damage (STR for Warriors), while the Secondary Stat is the one that yields less and is usually required to wear equipment (DEX for Warriors).

 Derivation

Since all the Max Damage formulae follow the exact same format of DM*(4 * PS + SS) * (Attack / 100),

DM*(4 * PS + SS) * (Attack + 1 / 100)

Let X = DM*(4 * PS + SS) / 100,

X * (Attack + 1)

X * Attack + X

DM*(4 * PS + SS) * (Attack / 100) + DM*(4 * PS + SS) / 100

Original Max Damage + DM*(4 * PS + SS) / 100

Therefore, the damage contributed by each point of WA or MA is given by DM*(4 * PS + SS) / 100.