Old school dice pools

So, I just had a fast combat/mass combat idea for D&D, probably from  Chainmail or Delta's blog:

Roll 1d6/level for fighters, half as much for clerics, 1/3 for MUs.

1 misses, 2-5 hit/miss depending on AC, 6 always hits. 

Monsters only need one hit per HD and we don't even need d20s. 

The idea is making combat against dozens of opponents a bit quicker.

But come to think of it, it could be pushed into an entire system. Let's see.

Duels

Two 9-HD fighters facing off would each roll 9d6 and cause an average of 3 hits per round (assuming they hit on a 5-6), so combat would be a bit quicker than, say, B/X.

Ranged combat

Both in real life and D&D, ranged combat is not usually as efficient as mêlée combat. Maybe adding 1 or 2 to AC is enough. To avoid treating an archer like a machine gun, you can rule "missed" shots are time spent in aiming, drawing, etc., and only "hits" or 1s waste arrows.

Against a single target, maybe all damage comes from a carefully aimed single arrow; so a very powerful fighter with a magic arrow could kill a dragon immediately, but this is very rare.

Weapons

Certainly there is some nuance lost here. Let's assume everyone is using a single-handed weapon. 2H weapons might add a dice, while maces may remove a point of AC, etc.

Turn Undead

Cleric rolls 2d6/level. 

Rolling 2-5 turns one HD of undead, 6 damages them. You can alter these numbers to make the cleric more or less powerful, or maybe make turn undead a spell (see below).

Spells

Casters have 2d6/level "magic dice" per day. 

When casting a fireball, it works identically as a fighter's attack, but any 6s you roll are removed from your pool until the next rest. 

(I think I got this idea from Necropraxis).

This fixes a number of fireball problems I usually have.

Same works for curing wounds.

But what about spells that deal no damage? Maybe we could still keep the "roll to cast" and "magic dice" aspects. a 4-6 counts as a success; a 1st level spell requires only one success to function, etc.

You can use several dice to cast a 1st level spell, so you can be sure it succeeds in the first try, but that way you'll also roll more 6s and spend more dice.

Skills

Let's use "hear noise" as an example. Non-thieves have 1-in-6 chances, thieves start with 2-in-6.

So let's say a normal PC rolls 1d6, but a thief adds 1d6/level. Rolling a single 6 means success, so the thief start with 30.5% chance. By level 10, he rolls 11d6, with a 85% chance of success. He won't get to 99% until level 19-20 or so, which is nice, so there is always some chance of failure.

Maybe multiple 6s mean extraordinary success, and rolling all 1s means disaster (e.g., falling from a climb or getting caught in a trap).

Backstabbing is easy; a thief simply attacks as a fighter while backstabbing, and maybe lowers the AC by one if you want them to be really deadly.

Saves

Saves can work similarly to skills. Everyone gets 1d6 plus 1d6/level. 

Notice that the progression from 30% to 85% between level 1 and 10 is quite fitting. You can give fighters, dwarves, paladins etc. an extra die or two.

You do not usually "save" against damage; treat this like an attack against AC (see below).

HP

There is no more HP, only "hits". To make things a bit softer, I'd give each PC one hit PLUS level for fighters, level/2 for clerics etc.

Maybe you could do the same for monsters so that a 1 HD monster has 2 hits and so on. 

AC

AC now is 2 (unarmored) to 6 (plate+shield). 

If you want magic armor etc. you could go even higher, but then you'd need special rules. For example, each time you roll a 6 you can roll again and add 5 to get a result from 6 to 11.

In conclusion...

Well, if you like dice pools, you can see that you might was well play old school D&D with them and a little conversion. But you'd lose some nuance in ability scores, weapons, etc. Maybe just sticking to the d20 is easier.

Still, we have some nifty systems for mass combat, and maybe skills, spells and saves, to experiment with.