Level-scaled combat and analysis

My last two posts focused on the combat system in D&D as written, and how the faults of the system, insignificant at low levels, will eventually cause combat to break down into boring slogs or equally boring routs.  Now, I want to take a closer and harder look at an alternative system I tossed out almost as a throwaway, but which is quickly growing on me.

I proposed recently that attack rolls could be determined by comparing the levels of the combatants, and applying the difference between them.  For example, a 6th level fighter against a 2nd level fighter would attack using the THAC0 or attack matrix of a 4th level fighter.  The lower level combatant attacks as 1st level, regardless of how many levels inferior he actually is to his opponent.  I suggested some adjustments for other classes, to reflect their lesser combat ability relative to fighters.

After a little more thought, it seems to me that it would function a lot more smoothly, and with fewer fiddly calculations at the margin, if it was based on an Attack Bonus framework rather than THAC0 or a class-and-level based attack table.  (A little more granularity would also be nice; i.e. spread out those +2 jumps into more frequent +1s.)  The Dark Dungeons retro-clone has calculated Attack Bonuses for each class and for monsters in a way that lines up pretty well with the attack tables from Classic D&D, with the aforementioned granularity, so I'll use those numbers.

Each Armor Class has a target number for a hit - for example, to hit AC9 a 10 must be rolled, and this remains constant regardless of class or level.  These numbers will be equivalent to the line of the attack table for 1st level characters, i.e. a THAC0 of 19.

When creatures or characters attack each other, compare their Attack Bonuses, and subtract the lesser one from the greater.  The one with the greater initial AB gets this difference as a positive modifier to his attack roll.  The lesser rolls unmodified.  In effect, the Attack Bonus of the lesser goes toward neutralizing much of the advantage of the greater.  If two AC9 characters are fighting, and one of them has an Attack Bonus one point higher than the other, one will need a 9 to hit, and the other a 10.

The upshot of all this is that a character fighting an evenly matched opponent is going to need about the same number to hit, whether he's 1st, 11th, or 21st level.  If he's fighting a much less skilled opponent, he's still going to be superior.  The greater the difference, the easier it is for him to hit.

Under this system, characters don't need to constantly upgrade their armor to try to keep pace with escalating attack rolls.  The thief's leather armor never becomes obsolete.  He's still lightly protected, as he was at the beginning.  Wearing light armor to maintain a rapid movement rate is no longer such a lopsided tradeoff.  A lightly armored swashbuckler is no more disadvantaged by her choice at 25th level than she was at 1st.  She doesn't need absurd magic items like bracers of defense AC 0 to make her style viable.  The game master doesn't have to slip into Monty Hall mode when handing out magic armor and protective gear.

With the AC arms race blunted, outrageous negative ACs will be far less common, allowing low level opponents to be more of a threat to high level PCs.

As I mentioned in the first post in this mini-series, high level combats are going to take longer when combatants aren't hitting and doing damage each round practically at will.  Using this system, it makes a lot of sense to compensate by increasing the damage potential of high level characters.  Weapon mastery, as detailed in the Master Set or the Rules Cyclopedia, fits into this system far better than it does in the original, in my opinion.  Escalating damage and increased frequency of hits together seem like massive overkill.  Alternatively, simply bumping up the damage potential of all weapons a class can use at certain levels will work just fine too.  The first upgrade might be to one die larger than the base damage, then to two dice one size lower than base damage, then to two base damage dice, then two dice one size larger than base.  1d4 becomes 1d6 becomes 2d3 becomes 2d4 becomes 2d6.   1d6 becomes 1d8 becomes 2d4 becomes 2d6 becomes 2d8, and so on.  Fighters and dwarves get upgrades at levels 6, 12, 18, and 24.  Clerics, thieves, elves, and halflings upgrade at 8, 16 and 24.  Magic-users upgrade at 12 and 24.

This system is also a natural fit with multiple attacks.  As written, there's no cost to multiple attacks, and no reason to choose a single attack if you have the option for multiples.  Consider the possibility that attacking multiple times means that you have to divide your Attack Bonus by the number of attacks, though.  Now, the choice to take extra swings will mean that you either sacrifice part of your advantage, or give a greater advantage to your opponent.  A fighter with an AB of 8 attacking a dragon with an AB of 10 once per round gives the dragon a +2 bonus to hit him.  If he attacks twice per round, the dragon's advantage becomes +6.  He certainly can rush the beast in a whirlwind of steel, but at the cost of being less able to defend himself.  If the fighter's Attack Bonus is 16 to the dragon's 10, his bonus to each attack would be +3 instead of +6.  In that case, he sacrifices accuracy to attack in a flurry.

It could also be used to make surprise attacks and missile attacks, which are hard to defend against, more deadly relative to ordinary melee attacks.  The attacker in those cases might get to use his full Attack Bonus unopposed, or opposed by only half the target's AB.  You'd definitely want to use rules to make firing into melee hazardous, or missile weapons would have an unqualified advantage over melee attacks.

Is this still D&D, or has it become something else?  Is it old school compatible?  I don't know, but I'd like to give it a try.