Depends how your game is set up. A 8 STR goblin wielding a 1D6 dagger against a Knight in 10 rPD armor that doesn't use hit location or activation rolls equal no damage at all.
Balance of DC versus DEF is critical in a game that doesn't have optional combat rules. As somebody who runs games only at the Heroic level (so far), I am well aware that a point or two (in either direction) off of the average can make a huge difference between a defending character laughing or gurgling in a pool of his own blood. The lower point your game, the more those variations make a difference.
So yeah, your setup is important, but a properly balanced Heroic game can be deadly. Optional combat maneuvers make it deadlier, but even lacking those, Heroic games are often deadly from attrition. That's not even accounting teamwork, multiple attacker bonuses, using terrain features and all the other unpredictable goodies that go with running a game.