Oh, almost forgot. Throw the points that are left in your clerics benediction. Then, if there is anything you cant dispell(like -50% damage debuff enenies sometimes give you), just leave 1 low dps monster alive and heal the debuffed party member until you get Benediction:)
I cant speak for the main campain, but for survival, getting a lvl 40 with a conjurer, warrior, ranger and a cleric is a piece of cake.
Warrir should have the best armour with as much health regen you can have and cleave.
Cleric should have heavy armour with 25+(including his base) mana regen, mass heal, regular heal, purify and revive.
Ranger should have the normal medium armours with a possible mana/health regen, but anything goes. He should also have Hail of arrows, pin and natures balm.
Conjurer should have mana regen stuff with Wargolem, Refresh energies, Call soul and Eldritch Aeigis.
At the beggining leave 1 monster alive(and heal ofcourse) and buff your party. Summon 2 war golems, put on Eldritch Aeigis, Nature Balm everyone and You are ready to go.
Its easy as hell. Just place your warrior in the middle in the 1st row, and everyone other in 2nd row. Dont forget to heal golems, although party's health goes first^_^
Piece of cake.