Calculating Stat vs Att/M.Att (Prime Scrolls)

Yes, you'll definitely have to consider your %stats. Not much with %ma as it is multiplicative to both your MA and stat portion of the formula(4P+S).

Removing multipliers and such:

(4P+S)*A=R

4P+S : A is what you need to be taking into consideration, where

P=Primary stat * (1+Primary%) + Primary stat that doesn't get affected by stat%
S= ^Replace primary with secondary
A=M/Attack

Edit: usually though your secondary stat is negligible, so it's simply P:A

i.e. Primary Stat : Attack / (1+Primary stat%)