why sometimes shield goblins take 1 damage, while everyone else takes normal damage ~12, do I just not have enough atk? They dont seem to be blocking it they just take 1 damage. Unless they were harmed by other goblins beforehand.

Im having trouble doing the caravan quest because of this 

Shield goblins and well anything with a shield take less damage because of their def stat, they will take 1 damage if their def is higher than your atk

What is your ATK level? 
I wouldn't start any combat heavy quest as a fighter until I have a sword, bow, and 10 ATK