Playing P/S/C/T, haven't chosen Light or Dark yet (not that far ahead). Right now, everyone is Lvl. 15. However, while the S is ready to train to Lvl. 18, the other three are able to train to Lvl. 20. I've always wondered why such a startling differentiation between the classes on this point. Or does the S going unconscious too much have anything to do with it? (I had Preservation on everyone, and so people kept getting knocked out by Wromthrax with horrifying negative HP that P or C was able to revive.) It does not seem like it would matter, but I am not sufficiently familiar with the internal mechanics of how this works.
And would this change depending on which quests have been completed? I've completed the first promotion quest for all but
the S, so would that be significant?
Differences in Learning skill level apply. Remember that Learning mastery (Expert/Master/GM) provide a multiplier to the skill level, so 10 points at GM Learning gives a 50% bonus iirc, while 10 points at basic learning gives a 19% bonus.
A character that is unconcious, dead, or stoned will not gain experience if a monster dies; the experience will be split among the living party members. I believe paralyzed characters still gain experience, even though they can't act. It doesn't matter how much damage is dealt to the monster while a character is dead, only who is alive once the monster hits zero hp.
The biggest difference is the class promotions. As rmeakins said, class promotions provide a party wide experience reward, but each character who is actually promoted (not just Honorary) gets an experience bonus on top of that. This is almost certainly the reason for the major difference in your case, assuming you haven't kill too many high XP monsters while party members were dead.
I thought of that. They were (at the time I posted) all at Skill Level 1. I have since raised the Sorc to 2, with the others remaining at 1. Hopefully he'll catch up.
If you want to keep experience roughly even, go ahead and boost the others to Learning skill level 2 as well.
That makes sense, as the others have (now) completed the initial promotion quests. The Sorc's is next.
Once the Sorc gets promoted, he should be at parity with the others.