I think that one problem is that the players are not familiar with higher level characters and campaigns. I've played in them, so I have a good feel as to what is a challenge or not, and I personally am very familiar with the cleric spell list.
Obviously, they do not work together as a team. It was especially blatant when we only had two players instead of the three now. The player mentioned was a kick down the door, run at 'em type of player. The other one was averse to danger with his aasimar cleric 7/paladin 2 and sorcerer 8 cohort. I have looked on in amazement as "fighter" player would run forward to be the only target against powerful enemies without any understanding with the other player that he would receive backup. The cleric/paladin's first reaction to any threat seems to be to cast searing light, when he's such a powerful combatant his first reaction should be to fight. I have been dismayed by the other player's fearfulness and inability to use his cleric effectively. The third player is more of a balance between caution and action. I would say that they have a poor ability to assess danger.
When the character went down AGAIN, the other characters said "We thought you were doing okay." based on their out-of-character knowledge. The player who lost three rounds to just getting helplessly wailed on didn't even say "I need help."
They really did not plan their attack on the drow headquarters well. They had a small army of freed slaves they were barely controlling, and their plan was to have them climb one by one into this cavern in the side of the chasm to attack an enemy that was ready for them. One PC and cohort in the front, another in the middle of the slaves, and two in the back for "crowd control". It didn't work too well. I finally just reminded the third player that he had a wand of fly.
I've realized that these guys are not very capable of handling anything too tough and that they really enjoy easy encounters. I have nerfed CotSQ to make it survivable and easier (that said, CotSQ's suggested starting level of 10 is laughable). Probably they don't have much experience with higher-level play, but we're playing CotSQ for now. Higher-level play is tough. I've made numerous hints to the cleric-player about spells, but they've gone unheeded. Now I'm just going to tell the players what to do in situations in which they're blatantly clueless. Still, the players often have good ideas, and the cleric's sorcerer cohort is the most powerful member of the party with some wicked spells choices.
I think 3.5 is complicated, and I said I'm happy to play a simpler system, but everyone likes their sourcebooks, you know.
Once somebody dies, they lose one proportional level with their new character, with a minimum level of 10. There has to be a penalty for dying. This penalty is just exacerbated when it gets applied successively.