Comparison to Standard ProcedureFor reference, the stock DMG damage expressions for a level 10 monster are 2d6+5 and 4d8+5 for normal and limited/encounter medium damage, respectively; high/brute damage takes those to 3d6+5 and 4d10+5. Those all pre-date the Monster-Manual 3 damage guidelines, so they're a bit on the low side. Sly Flourish's DM Cheat Sheet give us a more "modern" set of number at 2d8+9/2d8+13/2d8+17 for Medium/High/Limited damage. The spread for 2d8+17 is definitely a lot wider than 1d6+24 (+/- 27% versus +/- 8%).
While nice and simple, the amount of variance you get using the "Perkins Method" seems to change significantly across levels. I wonder if you couldn't get most of the way to a decent middle ground by using replacing the d6 depending on level -- for example using 1d4 for 1-5, 1d6 for 6-10, 1d8 for 11-15, etc. You'd still only have two dice, and you'd do a better job of keeping the variance constant relative to the total range (although I'm not certain how noticeable this variation would be). It certainly seems like a decent compromise, at the least.
Why Roll Damage At All?
One question The Id DM asked which I forgot to address (which may have been rhetorical) was "Why have damage rolls at all?" The answer is basically because D&D lacks a true "Margin of Success" system (hacks onto skill-checks such as using multiple DCs notwithstanding). Basically, hit tests are binary -- when you roll a hit, there's no obvious way to translate how much higher you were than the target's AC into a tangible result (assuming that would even be meaningful). If beat the AC by 1 or by 10, you still roll the same damage dice.
|D&D combat in a nutshell.|
Lots of other systems like Shadowrun, the Vampire/Storyteller System, and FUDGE work around this by using pools of dice and various mechanics for determining not just whether you succeed but by how much, and translating that directly into the result (in the case of combat, the damage done with the weapon). This has the nice property of requiring fewer rolls (although it's certainly debatable whether dice pools are actually "simpler" than d20) and getting rid of the weird artificial barrier between how good you are at hitting with a weapon (attack bonus) and how good you are at doing damage with it (damage bonus). Usually you see if you have any successes, and if so you count them up (and possibly multiply by your weapon's damage factor) to determine damage.
D&D on the other hand uses separate to-hit and damage rolls, kind of double-dipping into your character's statistics. First you hit to determine success, then you roll again to determine the "margin" of success. In one sense it's less intuitive ("I rolled a 30 vs 15AC but I only do 3 damage? WTF") but it does also give the designer a lot more flexibility with combat mechanics. For a fighter, increasing your STR mod by +1 means you're going to be more likely to hit, and when you do you'll hit harder; however it also allows for things like Weapon Finesse that let you increase your chances to hit by using your DEX modifier without necessarily turning you into a DEX-powered killing machine by letting you add it to damage as well. It's more complex on the surface, but also less "coupled" below the surface, helping to avoid unintended consequences.
Of course, none of this means you can't just use a constant amount of damage on a hit. But there is something to be said for accommodating the possibility of just barely hitting as well, and that starts to get harder to work in without some sort of decent MoS system.
What Would Gary Do?
Through all of this, I've been reminded of a discussion Paul at Blog of Holding recently shared resulting from his playing OD&D with one of the OD&Ders, Mike Monard:
What do hit points represent? Over the years, there have been a lot of ex post facto justifications for hit points, some by Gygax himself. In the end, as Mike says, "hit points are something to make combat go the way Gary wanted." That's a good thing to remember next time you find yourself tempted to jump in an internet argument about the subject.In other words, if it's doing what you want it to do and everyone is having a good time, go with it.
Seems like good enough advice to me.