I'll leave it up to readers to determine if stacking attribute is worth it or not.
I have a 213 MA staff with 143% electric attribute. MA of the staff is included in the total in each test, so don't add 213 to the 1050. Testing on Torobbies.
None of these are crits.
Staff of Thunder with 1050 MA should do 34850(?) damage (with the old formula).
What it does now with 143% electric attribute and 1050 MA: 39247
What it does now with 158% electric attribute and 1050 MA: 39708
What it does with 0% electric attribute and 1259 MA: 41956
Electro Attack with 1050 MA should do 25693(?) damage
What it does now with 143% electric attribute and 1050 MA: 30124
What it does now with 158% electric attribute and 1050 MA: 30586
What it does with 0% electric attribute and 1259 MA: 30973
As you can see for Electro Attack, the 143~158% electric attribute almost made up for 200 MA.