I think what you write is actually true. Taming the flames is better suited to two melee characters with fire resistance cooperating than a full party. This is actually true with many quests unless we have a strategy. If the fighters have to look after the squishies all the time then it's hard to deal with the enemies.
This is one reason why it's so important for at least one of the fighters to have the intimidate skill. The mobs will usually go after the PC doing the most damage. That's often the wizars / sorcerer due to wall of fire / ice storm etc. The cleric can get aggro too when using blade barrier, holy smite etc. If the fighter uses intimidate before the battle and gets a good hit against one of the monsters then he might get aggro and keep it despite the casters doing a lot of damage.
I think we get into trouble if we fight in open areas with the caster casting wall of fire. Then the caster will get initial aggro and the monsters will go straight for the caster. Usually the cleric is there too and will get aggro when the caster is dead.
So in order to counter such situations we need to have a good plan. E. g. we should try to fight in corridors where the fighters can block the way at the wall of fire. Then only monsters spawning behind the group will become a problem.
We completed 3 quests on elite with great success yesterday before we did taming the flames. Then we were working as a group and the casters were protected. Taming the flames is special because the monsters respawn all the time and that means there are no safe spots for the casters to hide. What happened yesterday was that the squishies retreated when the monsters broke through the fighters to attack the wizard. By doing that they ran into spawning monsters and were killed instantly. Then the fighters had to fight 3-4 fire elementals and that can be rather tough.
So the clue to success is to know how the monsters are working and plan accordingly. If we don't have respawning monsters then we should be able to do well. We can do level 5-6 quests on elite, level 7-8 on hard and 9+ on normal. If the quest is flagged as challenging we might have to get down on difficulty level.
The important thing is to learn from the mistakes we make and figure out how to improve out playing style. I think our optimal group will consist of the following characters: Fighter / barbarian, paladin, cleric, wizard / sorcerer, rogue, bard / ranger. We could have another caster instead of the bard / ranger if we need to do a lot of area of effect damage.
I notice a HUGE difference between having 1 melee character in the group vs 2 melee characters. When we have a less than full group (4 or less characters) we often have only one melee. That means the DPS will come from one character and that makes him quite vulnerable. I noticed that when Tom and I cooperated to strike the same monsters they went down quickly and we could move on to the next one. The best strategy in most quests is for all to strike against the same monster and switch to the next one. Each dead monster means less enemy DPS.
I think it's best to take out the support enemies before going after the boss. The boss can usually stand for quite awhile and that means the support monsters can do a lot of damage. The exception is when the boss is a caster. Then he MUST be taken down asap. When I analyze the battlefield I target the enemy casters first, then the enemy healers, then the enemy melee characters unless some characters have special abilities that can wipe a party (like earth elemental grab). So my paladin usually bypasses the enemy melee characters to get to the casters. When they're down the battle is much easier. Sometimes you need to take out the enemy healers first because you're unable to take out the casters fast enough. That happens sometimes on elite when they have more hitpoints.
I don't mind challenging quests. If we have a death or two then it proves we had to do our best to beat the quest. Then the reward feels better when we finally get the XP and loot. What IS frustrating are the situations where we have a good plan and still get wiped. We try again and the wipes continue and continue. That means you run out of options and pure luck will determine if you beat the quest or not. E. g. opening the chest before you die in taming the flames is pure luck. It can probably be done with an invisible rogue, but then you need high enough skills to avoid detection and you need luck with the evasions when you run back to the group. But the frustrating quest is now completed so we can look for more interesting quests.
The only "bad" thing about getting Kundarak favor level 1 with an extra personal bank tab (20 slots) is that I'm pretty sure Corwin will fill up these 20 slots in no time and still complain about a full inventory and no room in the bank.
I guess Corwin will at some time say he can't play because he doesn't have room for more loot and he doesn't want to sell any of the items already in his bank.
Then he will rely ask us to store his loot so he can continue playing. You get yet another tab in the personal bank when you get to level 2 favor with house K. So there is still hope for us to have enough room to hold Corwin's loot.