A THREAD FOR NEWCOMERS!

Please explain how the Defense and Offense skills work in relation to a hero's stats. I read that 1 Attack adds 5% to damage, and 1 Defense reduces damage by 2.5%. So, it seems that on Expert difficulty, these skills provide a bonus equivalent to 6 Attack or 6 Defense (6 x 5 and 6 x 2.5).
Basically, I want to know if they work based on the stats or in some other way?