i have played the game myself and i had at least 126.96.36.199.120 11:29, June 16, 2013 (UTC)
Overlord: Raising Hell - Numerical data for Defence
I've been testing the mechanics of Defence in Overlord: Raising Hell and while the exact formulae seems to be non-trivial, the following observations has been made:
Damage reduction provided by Defence seems to scale inversely with the power of attack (Arcanium Armour imbued fully with Browns reduces the damage received from regular mooks by more than half, but doesn't have any noticeable effect on highly damaging attacks).
Against vast majority of enemies each point of Defence improves overall life expectancy by roughly 1% (i.e. 50 points of Defence allows the Overlord to withstand 50% more hits).
I present below some numerical data I've collected: