Many Opponents, One Damage Roll

I've seen Michael Mornard (Old Geezer, on a couple forums) mention the way Gary handled fighter attacks against multiple opponents. The way most D&D players handle it: fighter gets one attack per level against 1 HD or less opponents. The way Gary apparently ran it: roll one die of any size, and if the result is less than or equal to your level, "that's how many orcs you killed." So, a 4th level Hero would roll a d4, a 6th level Myrmidon would roll a d6, an 8th level Superhero would roll a d8. Simple, because it reduces everything to one roll, although I, personally, would keep an attack roll. Just one attack roll, though.

I've been thinking about ways to use just a d6 for the second "damage" roll, though, instead of mixing up the die types. You could, of course, use 2d6 for characters above 6th level, and if the total is higher than the character's level, just use the higher of the two dice.

But even more compact, and with a little variability: Roll just 1d6. You are fighting X opponents, where X is less than or equal to your level. All but the last of your opponents (X - 1) are killed; the last opponent takes the d6 roll as damage (and thus might be killed, but might just be wounded.)