%attack vs %damage?

Assuming 300 attack, 4000 primary, 200 secondary and 1.3 multiplier.
9% attack:
1.3(4*4000+200)*(300*1.09)/100 = 68866

9% total damage:
1.3(4*4000+200)*300/100 = 63180 * 1.09 = 68866

there.
Shut up now about it.

Here it is, at its absolute core. Which is a comparison based on simple assumptions. Changing the stats would not make a difference. This is what Shinku means by a straight multiplication. HOWEVER. There is much more to it than this but it's much more complex.

We have boss damage, %damage skills, hacked weapons, and a bunch of other crap that make the changes rather unrealistic. There is another way to check for it but I don't know if it's worth doing