What chance? His combat style is such that if you're unfortunate to be the focus of attention while he's locked into close combat with you for 6 seconds worth of crashing-bashing-slicing-and-dicing you come away with less hit points (maybe from fatigue, maybe from injury, maybe using up your luck) unless you have at least some low-level damage reduction or regeneration. If you don't want to suffer that effect you'd best not be in melee with him. Similarly, if you don't want to take damage from a fire get some Fire Resistance or stay out of the fire.
Personally I'd like to see it fail to do any damage on a natural 1, to make the natural 1 have a little more meaning since it isn't a pure fumble anymore. That's how 13th Age handles it and it works well. Their explanation of "Damage on a Miss" is very clear and simulation / narrative based as well. Every PC does it with non-Nat-1 melee attacks, and some class options can increase that effective "damage floor" of a melee attack. The idea that a life-or-death melee engagement inevitably causes attrition of the stuff that keeps you alive (health, endurance, concentration, luck) round after round even if you avoid the brunt of the strikes is a glaring omission from D&D as a Combat Simulator.
Frankly, you probably have much better chances of coming through unscathed when taking a running leap through a narrow curtail of fire for half a second than you do going toe-to-toe with a powerful, trained killer trying to drop you with a sword (and any other instrument he has at his disposal - shield, hands, feet, shoulder, helmet) for 6 seconds but in many editions that's the exact opposite of how the mechanics play out - because they were putting Game Functions and Narrative ahead of Simulation. Setting up a wall of flames (magical or otherwise) requires more effort and they kept the rules for passing through hazardous areas relatively concise.
- Marty Lund