i accounted for that, if it weren't for toughness it would drain to 34% instead of the 57% it drained to.Diamond armour has an "armour toughness" value attached to it, no other armour does
Edit: Regen is the only possible cause, I tried the wood sword vs diamond armor thing and it would take 26 hits without armor piercing. so yea it's the regen

Thanks for allowing us to meet here!
Long time no see!