Okay, I just fought five of the six golems in de'Arnise Keep, killing them all with my kensai/mage/thief (Shadowkeeper for kensai) with Semi Multi Clerics Mod spells installed/learned/memorized as well. I'm also using the Widescreen Mod, the G3 Fixpack, G3 Tweaks, and aTweaks. What happened was that the mazed Minsc, Jaheira, Yoshimo, Aerie, and Nalia all gained no XP from this fight, while my main character gained her sixth of the (2000*2+8000*3)*1.1=30,800 XP. I don't expect this mod to be updated anymore, but for anyone reading this, if you notice something similar to this happening, you'll have to disable the script (after having enabled it at least once in the past, to get the uber ring and its amazing defensive effects, since monsters/NPCs could still target your banter or banter/support characters, although you ought to try to avoid that, if you really want a solo experience ;p) until you hit 100,000 TOTAL XP with a character, which means that, upon your convenience, you may enable it again, to have the 20,000 XP redistributed (don't wait forever, as it only gives those 20,000 XP chunks up to twice, while it continues to remove 20,000 XP chunks from scripted characters until they go below 100,000 total XP).
I've also had problems with characters mazing out and coming back over and over depending on various possibilities, often related to being outside (but also due to opening the de'Arnise Keep gate, which has NPCs scripted to come in and "help" you by "taking away" some of "your" XP (although I doubt the monsters would appear if you didn't do this) ;p), but restarting BG2 after saving AFTER the "problem causer" and loading that save often fixes this. I didn't test this well at all, and there could be many possible causes, and the ones I suggest may not be correct. In general the mod may be "inconsistent" depending on the overall mod install order or due to the mods you install. I can't give any better information than this, but if you can bear checking tag-along member XP before enabling the script (and then disabling it once it transfers XP) and sending tag-alongs off to where monsters/NPCs will target your main character instead of them (you could set their scripts to "None" so they don't attack enemies), this is still a good mod. May you have fewer problems than I. ;p