by Spectral Hand » Fri Jun 08, 2012 4:10 pm
My experience with multi-classing is that it is the dominant alternative once you get to moderate levels (5-6 or higher). After playing a lot of campaigns with these rules, almost everyone was multiclassing to "reset" their experience point table. Here is a broken example. Let's say you are playing an Attacker and you have just completed level 5 (you have 33,001 xp). If you continue as an Attacker for your next level, you'll be gaining 1% of weapon proficiency every 1800 xp (1800 xp is the interval for a level 6 Attacker). Alternatively, you could become a level 1 Warrior and increase your weapon proficiency by 1% every 100 xp. Obviously the latter choice is a better deal from a pure mechanics perspective.
After tinkering with a lot of options for how to "fix" this (and other issues related to balance between classes), we settled on the house rule mentioned in one of the other threads of making level function a flat function of xp (i.e., 10,000 xp per level). If you use this house rule, I'd recommend letting everything stack (i.e., including LP) with multi-classing.