Ok you ever have the situation where there is a multiclass character, like a fighter/cleric who just seems to be lacking behind the other characters? After DMing and playing multiclass characters for a while, I got to thinking, Acording to the PHHB a multicalss character pays the full amount of experience for each level, which ends up being double experience, since he splits the xp he earns evenly into 2 classes. Likewise a triple class character has to earn triple. Now I'm not about to argue that multiclass characters should advance at the same rate, but think about this for a moment. The xp cost of a class, theoretically includes such things as hit points, THACO, weapons, armor, saving throws, and proficencies, in addition to special abilities like spells and backstabing. However a multiclass character gets only one of the appropriate 'basic' abilities, he doesn't get 2 THACO progressions, and only the average hit points. generally he has to use the worst armor allowed, and sometimes the more limited weapons as well. Why then does he have to pay the experience cost for all of it?
Using the Guidelines for creating a new class in the DMG, I set out to creat the multiclass-class, ie a class that had all of the abilities and detriments of the appropriate multiclass, but was a single class. I could then compare this to the experience needed for the corresponding muticlass using the normal rules. I was hindered slightly by the fact that the rules in the DMG don't correspond to the normal experience progression. So first I had to create the basic classes. I will show the procedure I used for the widely used fighter/mage.
Fighter: Mage: Race: other +1 Race: other +1 Combat Value: Warrior +2 Combat Value: Wizard -1 Saving Throw: other 0 Saving Throw: Other 0 Hit Points: 1d10 +2.5 Hit Points: 1d4 +.5 Armor: All 0 Armor: None -1 Weapons: All 0 Weapons: Limited -1.5 HP after 9th: +3 +2 HP after 9th: +1 +.5 Proficiencies: 8 +2 Proficiencies: 5 +1.25 Fighter STR bonus +1 Fighter CON bonus +1 Weapon Specialization +3 Cast any school +16 Non human lvl lim 12 -.5 Non hum lvl lim 12 -.5 Total mods: 14 15.25 XP needed for 2nd: 2800 3050
Next I created the fighter-mage class:
fighter-mage: Race: other +1 Combat value: Warrior +2 Saving throw: other 0 Hit Points: (1d4+1d10)/2 =1d7=1d8 +1 Armor: none -1
Ok technically a fighter/mage knows how to use any armor, but if he wants to cast spells all he can use is a shield, so he has essientally no armor.
Weapons: All 0 HP after 9th: (+1 + +3)/2 = +2 +1 proficiencies: 8 +2 Fighter STR bonus +1 Fighter CON bonus +1 Cast any school +16 Non hum lvl lim 12 -.5 Total mods: 23.5 XP needed for 2nd 4700
Ok lets compare now, 4700/(2800+3050) = 80.3%. So it is obvious that a character would rather have the fighter-mage class than multiclas as a fighter/mage. Assuming that the ratio would hold true using whatever rules created the progressions in the PHB, this neans thhat the actuall progression for a fighter-mage should be (x2)(.80)=x1.6. In other words multiply the experience listed on the charts for each class by 1.6, then let the character put all of his earned experience into both classes, instead of splitting it like what the PHB says. This creates a character which should advance well with the rest of the single- classed party. It should be noted that this multiplier will be different for eachh class, some get a bigger or smaller break, the fither mage is about average. Remember that theh PHB methode counts some abilities twice, but it also counts some detriments twice as well, especially with mages and thieves. I have worked out a few of the other more common multiclasses.
fighter/thief x1.4 mage/thief x2.0 (no break here) fighter/cleric x1.4 cleric/mage x1.9 fighhter/mage/cleric x2.4 (as opposed to x3 for the PHB version)
Well hope this makes sense to anyone besides myself. I might add that I have tried these systems and they seem to work fairly well.