actually, its not better in heavy armor, the percentage of extra life is still the same.
If you wear heavy armor, you might be able to survive 11 hits instead of 10
in lgiht armor you would be able to survive 1,1 instead of 1 (yes, i know you cant make 0,1 hit, but you know what i mean)
The lgiht armor guy already chose to die quick, but this gives him a little extra life, and the same percentage extra life as an armored guy, and mgiht let him survive another horsebump or something.