In Irenicus´ dungeon, you should have found an Air Elemental scroll. If you summon it, it will take the dwarf out since the dwarf´s axe isnt magic so he cant hit the elemental.
And as accord said, first the mage and his familiar, then the thief (his backstabbs are terrible) and the barbarian, and the last the dwarf (if you havent used the elemental) cause he uses potions, so he will last more than the others
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"Let my spells do the dirty work" Ertai, High Sorceror of the Holy Flame