Even if normally there is no damage when the goblin fails to hit the swordsman, the swordsman has just gained some advantage, increasing his dominance in the battle. The goblin would have been better off never attacking... That is the problem I am trying to explain.The risk is rare. You’d only take damage on one of your attacks if the enemy rolled a critical. With Melee Skill 50 that would be 4% of rolls with a standard weapon. That’s a very low risk of taking damage on one of your attacks.
There are some creatures that are so skilled (champions) that you can take damage more, along with some weapons that double the crit chance. But they aren’t ubiquitous.