Hmm... The thief is an interesting suggestion. I'm not sure I quite see the merit in the thief, but you certainly must know something I don't (after all, you've been a poster here since the games came out, and have played through them multiple times). What do they bring to the table besides being less-powerful knights? I was thinking about an archer (possibly in addition to another mid-weight character). What's your opinion on them? I guess a good metric would be to compare the performance of two archers against that of a knight and sorcerer (both in close-combat and in spell firepower).
How did the druid seem to fall short for you?