Setting aside the specific case of fighter and goblin, this sort of thing is inevitable. The rules of D&D must balance verisimilitude with fun gameplay and ease of use. That balancing act will sometimes mean that verisimilitude takes a hit. In this case, the culprit is turn-based combat--a source of countless verisimilitude breaks, but I have trouble seeing how you could do a non-turn-based system that wouldn't wreak even greater havoc on ease of use.
In other cases (hit points, leveling up), verisimilitude is sacrificed for fun gameplay. Your PC doesn't die arbitrarily, and you get a sense of tangible progress through the campaign, and if that means people walking away from 100-foot falls or going from apprentice to archmage in the space of six months, we live with that.
And in still other cases, gameplay and ease of use are asked to make sacrifices for verisimilitude. This is why a bunch of 4E mechanics got the axe.
Ideally, of course, one looks for mechanics that naturally support all three elements. But there will always be some tradeoffs.