I do not want to spend time repeating others, so I will try not to...
Apparently this guy has been playing for 6 levels, is he having fun? If yes, then what is the problem?
Now, if his experiences are that he is constantly knocked out then I too would complain.
How about a few level drains on this guy, let him regain those levels and re-roll the last few hit dice as a result. Sure it would stink to loe two levels, but if he were to roll a 8, 10 for HP on the regained levels, then he might be happier. I know I would be.
Also, I do not even know if these items exist in 3e, but give him one of those books that give you experience. Basically level him faster than his cohorts. If he were to gain two levels on everyone else, the HP would come (hopeuflly higher than average this time) and even if they were only average, the higher BAB, saves, and abilities might be placing him above the others that way.
So he's a 9th level Bar with 56 hp while his buddy is a 7th level fighter with 57, but he should be getting the drop on this guy in combat.
g!