[Baalz]

Sure, try it with legions of steel cast - this is hardly a rare situation for Ulm. Towards the end of the curve extra protection is exponentially more effective because of the distribution curve of blows which will pierce it.

Look at it this way, a 10 str guy with a spear that does 3 damage will do 13 + open d6 damage. Very rough math here, but ballpark to do damage to a 20 protection unit the roll would have to be 8 over the die roll for the protection, so about 8% of hits will deal damage. To damage a 24 protection unit the roll will have to be 12 over, so a bit over 2% will inflict damage. So, adding 20% to the protection reduces the damaging blows by a factor of around 4.

Its not the rare colossal damage hits which bring down heavy infantry in numbers, it's the adding up of the 1 and 2 point hits as they get swarmed.