I have 501 attack and the increase on pies seem to be % based so thats why you are getting more of a boos than me.
And i agree you cant just multiply your attack and get your WS damage number but if the +24 i put on my weapon did increase my WS damage at all the difference was so small it just wasn't noticable as i was doing 820-830 crits before i equipped it and after i did.
Also have you done any Str testing? i need to get a 2nd set of armour made so i can test it myself but am curious to know if it directly affects any damage or if its just a set amount increases your attack power.